题目内容：
What does the author of the essay in the fourth paragraph want to say?
A．Efforts should be made to solve the problems of transportation of nuclear waste over longdistance. B．Efforts should be made to develop as many nuclear disposal sites in the US as possible.
C．Efforts should be made to develop nuclear disposal sites to suit the circumstances of the region.
D．Efforts should be made to build up temporary nuclear disposal sites as possible.
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答案解析：