--Let' s go to the concert tonight, Mary.--Sorry, I_____. I have

--Let' s go to the concert tonight, Mary.
--Sorry, I_____. I have to help my morn with the housework.
A、needn't
B、can' t
C、mustn't
D、shouldn't
【正确答案】：B
【题目解析】：needn't 表示不需要，mustn't，shouldn't 表示禁止，不应该，can't 表示不能，根据题意选B