完形填空。
The population problem may be the __1__ one of the world today. The world's population is growing __2__ . Two thousand years ago, there were only 250 million people __3__ the earth. Four hundred  years ago, the number was __4__ 500 million. But at the beginning of the __5__ century, the world's  population was about l, 700 million.  In 1970, this number was 3,600 million. In 1990, the number was  five billion. A __6__ report says that the world population will __7__ six billion by the end of the 20th  century. This is just ten __8__ after it __9__ five billion. People say that by the year 2010, __10__ may  be seven billion.
(    ) 1.  A. great                 (    ) 2.  A. faster and faster     (    ) 3.  A. in                     (    ) 4.  A. hardly                 (    ) 5.  A. twenty                 (    ) 6.  A. USA                   (    ) 7.  A. past                   (    ) 8.  A. weeks                 (    ) 9.  A. get                   (    ) 10. A. this	B. greater             B. fast and falt       B. on                 B. more               B. twelve             B. UN                 B. pass               B. months             B. gets               B. its	C. greatest             C. fastest and fastest C. at                   C. almost               C. twentieth           C. PRC                 C. passed               C. seasons             C. reached             C. one	D. greating             D. faster and fast     D. for                 D. over                 D. twelfth             D. PLA                 D. passes               D. years               D. reach               D. it