问题描述：
[求助]高中英语单选题,谢谢了
The chief reason for the population growth isn't so much a rise in birth rates____a fall in death rates as a result of improvements in medical care.A.and B.as C.but D.or,为什么选B,我觉得应该选C啊!求解啊,谢谢
The chief reason for the population growth isn't so much a rise in birth rates____a fall in death rates as a result of improvements in medical care.A.and B.as C.but D.or,为什么选B,我觉得应该选C啊!求解啊,谢谢
问题解答：
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