The population problem may be the
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. 第一个空为什么不能填great?第二个空为什么填fast and fast?第八个空为什么要填years?第九个空为什么填reached?第十个空为什么不能填this?