You must a wide vocabulary if you want to learn a language well. A. build upB. put on C.

问题补充：

You must a wide vocabulary if you want to learn a language well.

A. build up

B. put on

C. settle down

D. set up

答案：

(答案→)A. build up

B. put on

C. settle down

D. set up

解析：考查动词短语辨析。A加强；B增强；B穿上；C定居；D建立。句意：如果你想学好一门外语就必须增加词汇量。根据句意说明A正确。