8.difficult 9.with 10.happening(stop...from doing)意为“阻止/防止……去做某事”)
(2)
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 1,700 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, 1 0
may be seven billion.