单项选择题

Making energy use completely harmless to the environment（）very difficult and usually economically expensive.

A.is
B.are
C.have been
D.shall be

<上一题 目录 下一题>
热门 试题

单项选择题
Some members of the committee suggested that the meeting（）.

A.being postponed
B.to be postponed
C.be postponed
D.postponed
单项选择题
（）no gravtity,there would be no air around the earth,hence no life.

A.If there had been
B.If there was
C.Had there been
D.Were there
相关试题