This is important book. It helped me a lot in old days.A. a; anB. an; theC. the; anD. /;

问题补充：

This is important book. It helped me a lot in old days.

A. a; an

B. an; the

C. the; an

D. /; the

答案：

A. a; an

(答案→)B. an; the

C. the; an

D. /; the

解析：句意：这是一本重要的书，在旧社会它帮助了我许多。不定冠词a/an表示某一类人或某事物中的任何一个,经常用在第一次提到某人或某物时,用不定冠词起介绍作用，表示一个。a用于辅音音素前an用于元音因素前。important元音因素开头，in the old days ,在过去，在以前。故选B。