托福考试

【单选题】Questions 11-22Avicolturists, people who raise birds for commercial sale, have not yet learnedhow to simulate the natural incubation of parrot eggs in the wilD、They continueto look for better ways to increase egg production and to improve chick survival rates.line When parrots incubate their eggs in the wild, the temperature and humidity of the nest are controlled naturally. Heat is transferred from the bird’s skin to the top portionof the eggshell, leaving the sides and bottom of the egg at a cooler temperature. Thistemperature gradient may be vital to successful hatching. Nest construction cancontribute to this temperature gradient Nests of loosely arranged sticks, rocks, or dirtare cooler in temperature at the bottom where the egg contacts the nesting material.Such nests also act as humidity regulators by allowing rain to drain into the bottomsections of the nest so that the eggs are not in direct contact with the water.As thewater that collects in the bottom of the nest evaporates, the water vapor rises and isheated by the incubating bird, which adds significant humidity to the incubationenvironmentIn artificial incubation programs, aviculturists remove eggs from the nests of parrotsand incubate them under laboratory conditions. Most commercial incubators heat theeggs fairly evenly from top to bottom, thus ignoring the bird’s method of naturalincubation, and perhaps reducing the viability and survivability of the hatching chicks.When incubators are not used, aviculturists sometimes suspend wooden boxes outdoors to use as nests in which to place eggs. In areas where weather can become cold aftereggs are laid, it is very important to maintain a deep foundation of nesting material toact as insulator against the cold bottom of the box. If eggs rest against the woodenbottom in extremely cold weather conditions, they can become chilled to a point wherethe embryo can no longer survive. Similarly, these boxes should be protected fromdirect sunlight to avoid high temperatures that are also fatal to the growing embryo.Nesting material should be added in sufficient amounts to avoid both extremetemperature situations mentioned above and assure that the eggs have a soft, secureplace to rest. According to paragraph 2, when thetemperature of the sides and bottom of the eggare cooler than the top, then
A、there may be a good chance forsuccessful incubation
B．the embryo will not develop normally
C．the incubating parent moves the egg toa new position.
D．the incubation process is slowed down

网考网参考答案：A
网考网解析：
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