Question

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

Answer 1

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...

Answer 2

选D don't have to 没必要，不用
You don't have to （pay for the telephone call).
你没有必要付。因为是免费的

Answer 3

选择D
How much shall I pay for the telephone call?
You 【don't have to】. It is free.
打电话多少钱？
你不需要付钱，是免费的。

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