How much shall I pay for the telephone call?You ( ).It is free.

题目

How much shall I pay for the telephone call?You ( ).It is free.
A.shouldn't B.may not C.mustn't D.don't have to

答案

D.你不必要（付钱）——don't have to是“不必要”的意思,在此符合语境
A.你不该...B.你可能不...C.你不准...