—Let's go to the concert tonight, Mary.—Sorry. I _____, I have t

—Let's go to the concert tonight, Mary.—Sorry. I _____, I have to help my mom with the housework.
A、needn't
B、can't
C、mustn't
D、shouldn't
【正确答案】：B
【题目解析】：表示我不能，I can't句意：对不起，我不能，我得帮妈妈做家务。