N₂表示氮气，还可以表示（　　）

①氮元素；②一个氮分子；③两个氮元素；④氮气由氮元素组成；⑤每个氮分子由两个氮原子构成；⑥两个氮分子．

A．②④⑥

B．①③⑤

C．②④⑤

D．①④⑤

(2014·济南4月巩固性训练)________it is，the boy never seems to be able to finish it off.

A．However interesting a book

B．Whatever interesting a book

C．How interesting a book

D．What an interesting book