American Race to the Moon
The roots ofAmerica’s plan to land a man on the moon can be found outside of the country.Although never directly mentioned in its official motto, the NationalAeronautics and SpaceAdministration (NASA、was established as a direct result of the Soviet space program’s successful launching of Sputnik 1, the first man-made satellite, on October 4th, 1957. The U.S.Congress, worrying that the country was about to lose its technological edge over the rest of the world, demanded drastic action.Dwight
D、Eisenhower, then president, waited only a few months before creating a new government agency responsible for all non-military activity in space. On July 29th, 1958, the president signed the NationalAeronautics and SpaceAct, creating NASA、The outside world continued to have an effect. The technology initially used by NASA、came in large part from the German rocket program of the Second World War. Wernher vonBraun, who was recruited by theAmericans at the end of the war, is today considered the father of the United States space program.
NASA、began operations on October 1st, 1958, and was made up of four laboratories as well as about eight thousand employees from the already 43-year-old NationalAdvisoryCommittee forAeronautics. The history of the new organization can be divided into various phases, each related to a specific program. The first experiments undertaken as part of Program Mercury were designed simply to discover if humans could actually survive a round-trip voyage into space. This involved the construction of 20 spacecraft, each large enough to hold one astronaut. On a very basic level, NASA、needed to test what worked and what didn’t. They made numerous unmanned launches, many of them resulting in explosions, as well as four separate launch attempts that included small creatures. The first was a small monkey.By 1961, NASA’s Program Mercury successfully placedAlan Shepard into space, but for only fifteen minutes.
This milestone quickly led to theApollo Project. The initial idea was to get a human close to the Moon, but not actually on it. There were too many unknowns about the surface of the Moon to plan a safe landing. On February 20th, 1962, John Glenn piloted the Friendship 7 for five hours in orbit around theEarth. NASA、had finally learned how to get a human into space, and most importantly, keep him there. This was the crucial step necessary: they had created the ability to stay in space long enough to really figure out what to do there. The objectives of the mission changed drastically, however, when President JohnE、Kennedy told the nation on May 25th, 1961, thatAmerica would instead focus on a manned mission to and from the Moon, and that these missions would be possible by the end of the decade.
■
A、Many people worried about the money that would be spent, feeling that it would be better used for other purposes. ■
B、Others continued to see the program in relation to the rest of the worl
D、■
C、They worried that NASA、did not seem to have any valuable military use and openly questioned the idea of spending money on rockets that could not be used to defend the country. ■
D、Kennedy managed to convince both sides of the project’s benefits. He assured people that the mission would provide jobs and resources to different states throughout the country as well as specific advances in rocket technology. Kennedy stressed the value of dual-use technology, which could be used for both military and non- military purposes.
Instead of sending a person to space and back again, which required only one lift-off fromEarth followed by a landing, theApollo Project now entailed anEarth lift-off, followed by a landing on the Moon, another lift-off, and then a finalEarth landing. The Gemini Program, therefore, was created to collect information and perfect techniques that would make theApollo Project possible. U

Human Migration
Human migration: the term is vague. What people usually think of is the permanent movement of people from one home to another. More broadly, though, migration means all the ways—from the seasonal drift of agricultural workers within a country to the relocation of refugees from one country to another.
Migration is big, dangerous, and compelling. It is 60 millionEuropeans leaving home from the 16th to the 20th century. It is some 15 million Hindus, Sikhs, and Muslims swept up in a tumultuous shuffle of citizens between India and Pakistan after the partition of the subcontinent in 1947.
Migration is the dynamic undertow of population change: everyone’s solution, everyone’s conflict.As the century turns, migration, with its inevitable economic and political turmoil, has been called "one of the greatest challenges of the coming century".
But it is much more than that. It is, as has always been, the great adventure of human life. Migration helped create humans, drove us to conquer the planet, shaped our societies, and promises to reshape them again.
"You have a history book written in your genes," said Spencer Wells. The book he’s trying to read goes back to long before even the first word was written, and it is a story of migration.
Wells, a blond geneticist at Stanford University, spent the summer of 1998 exploring remote parts of Transcaucasia andCentralAsia with three colleagues in a Land Rover, looking for drops of bloo
D、In the blood, donated by the people he met, he will search for the story that genetic markers can tell of the long paths human life has taken across theEarth.
A、[■]But however the paths are traced, the basic story is simple: people have been moving since they were people.
B、[■] If early humans hadn’t moved and intermingled as much as they did, they probably would have continued to evolve into different species.
C、[■] From beginnings inAfrica, most researchers agree, groups of hunter-gatherers spread out, driven to the ends of theEarth.
D、[■]
To demographer KingsleyDavis, two things made migration happen. First, human beings, with their tools and language, could adapt to different conditions without having to wait for evolution to make them suitable for a new niche. Second, as populations grew, cultures began to differ, and inequalities developed between groups. The first factor gave us the keys to the door of any room on the planet; the other gave us reasons to use them.
Over the centuries, as agriculture spread across the planet, people moved toward places where metal was found and worked to centers of commerce that then became cities. Those places were, in turn, invaded and overrun by people in later generations called barbarians.
In between, these storm surges were steadier but similarly profound tides in which people moved out to colonize or were captured and brought in as slaves. For a while the population ofAthens, that city of legendary enlightenment was as much as 35 percent slaves.
"What strikes me is how important migration is as a cause and effect in great world events. " Mark Miller, co-author of TheAge of Migration and a professor of political science at the University ofDelaware, told me recently.
It is difficult to think of any great events that did not involve migration. Religions spawned pilgrims or settlers; wars drove refugees before them and made new land available for the conquerors; political upheavals displaced thousands or millions; economic innovations drew workers and entrepreneurs like magnets; environmental disasters like famine or disease pushed their bedraggled survivors anywhere they could replant hope.
"It’s part of our nature, this movement," Miller said, "It’s just a fact of the human condition. " Look at the four squares [■] that indicate where

Fighting in Nature
In nature, fighting is such an ever-present process that its behavior mechanisms and weapons are highly developeD、Almost every animal capable of self-defense from the smallest upwards fights furiously when it is cornered and has no means of escape.
However, in another respect the fight between hunter and hunted is not a fight in the real sense of the word: the stroke of the paw with which a lion kills his prey may resemble the movements that he makes when he strikes his rival, but the inner motives of the hunter are basically different from those of the fighter. The buffalo which the lion fells provokes his aggression as little as the appetizing turkey which I have just seen hanging in the larder provokes mine. The difference in these inner drives can clearly be seen in the expression movements of the animal: a dog about to catch a hunted rabbit has the same kind of excited happy expression as he has when he greets his master or awaits some longed-for treat. Growling, laying the ears back, and other well-known expression movements of fighting behavior occur when predatory animals are afraid of a wildly resisting prey, and even then the expressions are only suggesteD、
The opposite process, the counter-offensive, of the prey against the predator, is more nearly related to genuine aggression. Social animals in particular take every possible chance to attack the eating enemy that threatens their safety. This process is called "mobbing". The survival value of this attack on the hunter is self-evident.Even if the attacker is small and defenseless, he may do his enemy considerable harm. For example, if a sparrow hawk is pursued by a flock of warning wagtails, his hunting is spoiled for the time being.And many birds will mob an owl if they find one in the day-time, and drive it so far away that it will hunt somewhere else the next night.
In some social animals such as jackdaws and many kinds of geese, the function of mobbing is particularly interesting. In jackdaws, its most important survival value is to teach the young inexperienced birds what a dangerous eating-enemy looks like, which they do not know instinctively. For just such educational reasons, geese and ducks may gather together in intense excitement to learn that a fox—anything furry, red-brown, long-shaped and slinking—is extremely dangerous.
Besides this didactic function, mobbing of predators by jackdaws and geese still has the basic, original one of making the enemy’s life a burden. Jackdaws actively attack their enemy, and geese apparently intimidate it with their cries, their thronging and their fearless advance. The greatCanada Geese will even follow a fox overland in a close phalanx, and I have never known a fox in this situation try to catch one of his tormentors. With ears laid back and a disgusted expression on his face, he glances back over his shoulder at the trumpeting flock and trots slowly—so as not to lose face—away from them.
Among the larger, more defense-minded grazing animals which en masse are a match for even the biggest predators, mobbing is particularly effective;A、[■]According to reliable reports, zebras will molest even a leopard if they catch him on plain where cover is sparse.B、[■] Once, when I was out with my dog, I was obliged to jump into a lake and swim for safety when a herd of young cattle half encircled us and advanced threateningly;
C、[■]And when he was in Southern Hungary during the First World War, my brother spent a pleasant afternoon up a tree with his Scotch terrier under his arm, because a herd of half-wild Hungarian swine, disturbed while grazing in the wood, encircled him.D、[■] Fortunately, the swine dispersed after they confirmed that my brother and his dog were not offensive.
The word instinctively in Paragraph 4 is closest in meaning to______.
A、clearly

THE、CIRCULATORY SYSTEM OF TREES
1 Inside the tree’s protective outer bark is the circulatory system, consisting of two cellular pipelines that transport water, mineral nutrients, and other organic substances to all living tissues of the tree. One pipeline, called the xylem--or sapwood--transports water and nutrients up from the roots to the leaves. The other, the phloem--or inner bark---carries the downward flow of foodstuffs from the leaves to the branches, trunk, and roots.Between these two pipelines is the vascular cambium, a single--cell layer too thin to be seen by the naked eye. This is the tree’s major growth organ, responsible for the outward widening of the trunk, branches, twigs, and roots.During each growing season, the vascular cambium produces new phloem cells on its outer surface and new xylem cells on its inner surface.
2 Xylem cells in the roots draw water molecules into the tree, taking in hydrogen and oxygen and also carrying chemical nutrients from the soil. The xylem pipeline transports this life-sustaining mixture upward as xylem sap, all the way from the roots to the leaves. Xylem sap flows upward at rates of 15 meters per hour or faster. Xylem veins branch throughout each leaf, bringing xylem sap to thirsty cells. Leaves depend on this delivery system for their water supply because trees lose a tremendous amount of water through transpiration, evaporation of water from air spaces in the leaves. Unless the transpired water is replaced by water transported up from the roots, the leaves will wilt and eventually die.
3 How a tree manages to lift several liters of water so high into the air against the pull of gravity is an amazing feat of hydraulics. Water moves through the tree because it is driven by negative pressure--tension--in the leaves due to the physical properties of water. Transpiration, the evaporation of water from leaves, creates the tension that drives long- distance transport up through the xylem pipeline. Transpiration provides the pull, and the cohesion of water due to hydrogen bonding transmits the pull along the entire length of xylem. Within the xylem cells, water molecules adhere to each other and are pulled upward through the trunk, into the branches, and toward the cells and air spaces of the leaves.
4 Late in the growing season, xylem cells diminish in size and develop thicker skins, but they retain their capacity to carry water. Over time the innermost xylem cells become clogged with hard or gummy waste products and can no longer transport fluids.A、similar situation occurs in the clogging of arteries in the aging human body. However, since the vascular cambium manufactures healthy new xylem cells each year, the death of the old cells does not mean the death of the tree. When they cease to function as living sapwood, the dead xylem cells become part of the central column of heartwood, the supportive structure of the tree.
What are the primary components of the tree’s circulatory systemA．Water, minerals, and organic substances
B．Xylem and phloem
C．Leaves, branches, and trunk
D．Roots and heartwood

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