III. 完形填空： Many of the world's pollution problems have been 1   by the crowding of large groups of people into cities．Supply for the2    of the people leads to 3   pollution by industry．If the4   increase in human population 5   at the present rate（比率），there may be much greater harm． Some scientists speak of the6   in number of people as“population pollution．” About 2000 years ago，the world 7  was probably about 250 million．8   reached a billion in 1850．By 1930the population was two billion．It is 9     six and a half billion．It is10   to double by the year 2050．If the population continues to grow at the same 11   ， there would be 25 billion people in the world a hundred years from now． Man has been using the earth's 12   more and more rapidly over the years．Some of them are almost13   ．Now many people believe that man's greatest 14   is how to control the growth of his population．The15   in the world will not support the human population，in time to come，if the 16   rate of increase continues． 17   there is over crowding in the 18   and hunger in some countries． Can man's rate of increase19   ？Many people believe that human survival（继续生存）in the future depends on the answer 20   the question． 1．A．made B．caused     C．led   D．worked out 2．A．needs B．satisfies   C．service     D．lacks 3．A．farther      B．less  C．further     D．better 4．A．harmful     B．small C．slow D．rapid 5．A．stops  B．continues C．slows down     D．adds to 6．A．increase     B．reduce     C．quality     D．quantity 7．A．people B．situation  C．population      D．land 8．A．They  B．You  C．We   D．It 9．A．now   B．in the past C．in the future    D．then 10．A．hoped B．expected  C．wished  D．looked forward to 11．A．time B．year C．rate  D．period 12．A．place B．oil    C．mines      D．resources 13．A．missed     B．rich  C．gone D．enough 14．A．problem  B．power      C．plan D．idea 15．A．food B．electricity C．energy     D．materials 16．A．past  B．present    C．future      D．slow 17．A．Already   B．Yet   C．Still D．Often 18．A．villages   B．mountains C．cities D．farms 19．A．continue  B．exist C．fall   D．keep 20．A．in    B．of    C．to     D．for