Both of my parents insist a computer for me but I don’t think it is necessary.A. to buyB

问题补充：

Both of my parents insist a computer for me, but I don’t think it is necessary.

A. to buy

B. on buying

C. buying

D. in buying

答案：

A. to buy

(答案→)B. on buying

C. buying

D. in buying

解析：insist on doing sth.是固定搭配的短语，on为介词，后面动词接ing形式。所以正确答案为B