-What do you think of the grammar book? -Oh, it really is useful reference book,

－What do you think of the grammar book?

－Oh, it really is _________ useful reference book, which is worth reading _________ second time．

a; a

an; the

an; a

the; the

试题答案

答案：A

a useful reference book表示“一本有用的参考书”，useful的第一个发音是［ju：］，属辅音开头，故用a; a second time表示“又一次”，作状语，故用不定冠词a。