单项选择题

Those countries were once worried that they would not have adequate supplies of petroleum.

A. effective
B. efficient
C. potential
D. sufficient
<上一题 目录 下一题>
热门 试题

单项选择题
It remains a puzzle about why our outermost planet exists.
A. problem
B. mystery
C. question
D. point
单项选择题
It is not clear whether the increase in reports is stemmed from greater human activity or is simply the result of more surveys.
A. flows
B. comes
C. derives
D. originates
相关试题