People in the 18th and 19th centuries used to sleep about 9.5 hours a night because they h
正确答案
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People in the 18th and 19th centuries used to sleep about 9.5 hours a night because they had ______.
A.no drive or ambition
B.no electric light
C.the best sleep habits
D.nothing to do in the evening
请帮忙给出正确答案和分析,谢谢!
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正确答案:B
根据第二段第一句"Thebeginningofoursleep-deficitcrisiscanbetracedtotheinventionofthelightbulbacenturyago",就可断定B为正确答案。而A明显不对;C是结果而非原因;D并非真正原因。
