By the year 2000, today's "have not" nations will have a total population of 5 billion people, nearly four fifths of the world's population.
Food isn't the only problem that such a population explosion presents. The more people there are and the worse their living conditions, the greater grow the possibility of all kinds of social problems.
In 1830, world population reached 1 billion. It took only 100 more years to add another billion to world population; just 30 more to add a third billion. And it took just 15 more years to reach the 4 billion mark in 1975. Actually, the world's birth rate is falling. But so is death rate, as medical advances have made it possible for man to live longer than before. Such advances have also reduced baby death rate. Unless population growth is reduced, the world population may reach 12 billion in a century. Is the earth capable of providing a good life for so large a population?
A population explosion will lead to ______.
A.a lot of social problems
B.medical advances
C.a decrease in food production
D.a worse life in every nation with 3 billion
第1题
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第6题
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C.重复实验,找出原因,修正假设,再进行实验验证
D.被动等待导师分配新任务
第7题
A.立即终止实验,再重新去寻找其他的科学问题
B.坚持发表没有被验证的科学假设
C.重复实验,找出原因,修正假设,再进行实验验证
D.被动等待导师分配新任务
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