英语完形填空 Many of the world's pollution problems have been caus

英语完形填空
Many of the world's pollution problems have been caused by the crowding of large groups of people into cities.Satisfying the 21 of the people leads to further polluting by industry.If the rapid increase in human population 22 at the present rate (比率),there may be much greater harm.Some scientists speak of the 23 in number of people as "Population Pollution".     About 2000 years ago,the world 24 was probably about 250 million.It reached a billion in 1850.By 1930 the population was two billion.It is 25 three and a half billion.It is expected to double by the year 2000.If the population continues to grow at the same 26 ,there would be 25 billion people in the world a hundred years from now.     Man has been using the earth's 27 more and more rapidly over the years.Some of them are almost gone.Now many people believe that man's greatest 28 is how to control the growth of this population.The materials in the world will not support the human population in time to come if the present rate of increase continues.29 there is over crowding in the cities and hunger in some countries.Can man's rate of increase continue?     Many people believe that human survival (幸存者) in the future 30 on the answer to the question.   21needs    supplies    service    supports   22 stops     continues     slows down      adds to 23 increase     reduce     country     improvement 24 people    situation     population     land  25 now     in the past     in the future     then 26 place     time     rate     result 27 oal     oil     mines     resources 28 problem     power      plan     idea 29 Already    Yet    Still    Often 30 feeds    lives    keeps   depends  

21needs
22 continues
23 increase
24 population
25 now
26 rate
27 resources
28 problem
29 Already
30 depends