I don't mind telling you the seret . you____(mustn't/needn't)it's not my fault why ____(should/can)i say sorry to the customer

I don't mind telling you the seret . you____(mustn't/needn't)it's not my fault why ____(should/can)i say sorry to the customer
I don't mind telling you the seret . you____(mustn't/needn't)
it's not my fault why ____(should/can)i say sorry to the customer

I don't mind telling you the seret . you____(mustn't/needn't)it's not my fault why ____(should/can)i say sorry to the customer
mustn't.虽然不知道后面接的是什么,但是可以确定填mustn't.
should是应该的意思.不是我的错,我为什么要跟顾客道歉呢?