–What did your parents think about your decision?–They always let me do I think I should.

问题补充：

–What did your parents think about your decision?

–They always let me do I think I should.

A. when

B. that`

C. how

D. what

答案：

A. when

B. that`

C. how

(答案→)D. what

解析：what（表示关系）（所）……的.Everyone should do what he thinks right.每个人都应该做自己认为是正确的事情。此外I think作插入语。