题目内容:
The problem of underground water is more serious because( )
A. the underground water trickles away all the year round B. the underground water is hidden deep beneath the Earth
C. the change of it must be controlled by the NASA's satellites Ψ考试大>在线Ψ考试中心Ψ
D. the dramatic change of it might affect the gravitational field
参考答案:
答案解析: