问题描述:

单选题

Building a reservoir indeed costs us a great amount of money, but in the long run it is greatly ________ to us, especially when we meet drought days.A.beneficialB.influentialC.commercialD.efficient

网友答案:
A解析beneficial“有益的”;influential“有影响的”,后接介词on; commercial“商业的”;efficient“有效率的”。
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