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 the 2 of the people leads to 3 pollution by industry．If the 4 increase in human population 5 at the present rate（比率），there may be much greater harm． Some scientists speak of the 6 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 is 10 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 almost 13 ．Now many people believe that man's greatest 14 is how to control the growth of his population．The 15 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 increase 19 ？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