Question

no,you didn't,等于,no,you don't have吗?

Must I go to the supermarket now?的否定回答应用No,you mustn't.还是No,you don't have to.
加原因.

Answer 1

否定回答应该是：No,you don't have to.

Must I go to the supermarket now?
我现在得去超市吗?
No,you don't have to
不,你不用去.

mustn't 表示禁止,不准.（所以不正确）

保证准确率~