Question

The European Union countries were once worried that they would not have ____ supplies of petroleum.

A) proficient B) efficient C) potential D) sufficient 为什么不能B 要选D 呢？

Answer 1

B efficient adj.有效率的，（直接）生效的，能干的
D sufficent adj. 足够的，充足的；
因此D更符合语境。
翻译：欧盟国家曾经担心他们得不到足够的石油供应。