This dictionary is very useful. It has many problems about words and idioms for me.A. loo

问题补充：

This dictionary is very useful. It has many problems about words and idioms for me.

A. looked up

B. kept up

C. taken up

D. cleared up

答案：

A. looked up

B. kept up

C. taken up

(答案→)D. cleared up

解析：cleared up= solve 意思是：解释，解答.