阅读文章，选择正确答案，回答问题。 the world’s population continues to grow. there are now about 4 billion of us on the earth. that could reach 6 billion by the end of the century and 11 billion in a further 75 years. experts have long been concerned about such a growth. where shall we find food, water, jobs, houses, schools or health care for all these people? a new study shows that the situation maybe changing. a large and raped drop in the world’s birth rate has taken place during the past 10 years. families generally are smaller now than they were a few years ago. it is happening in both developing and industrial countries. researchers said that they found a number of reasons for this. more men and women are waiting to be married and are using birth control methods to prevent or
