－How much shall I pay for the phone call?－You . This is free of charge.A. shouldn’tB. can’

问题补充：

－How much shall I pay for the phone call?

－You . This is free of charge.

A. shouldn’t

B. can’t

C. needn’t

D. mustn’t

答案：

A. shouldn’t

B. can’t

(答案→)C. needn’t

D. mustn’t

解析：由后面的This is free of Charge。可以知道答案。