Question

you used to play the piano ._____A usedn't she B didn't she

Answer 1

you used to play the piano ._____A usedn't she B didn't she
你给的试题和选项，人称不一致，不能选择。
正确表达应该是：
You used to play the piano ,didn't you/usedn't you?
或
She used to play the piano ,didn't she/usedn't she?
原因：
used to，作为情态动词，反义问句本身可使用两种形式：didn't sb/usedn't sb
祝你开心如意！

Answer 2

两个答案都不对。应该是: you used to play piano. didn't you ?

Answer 3

应该是didn't you，used to do 表示过去常常，这里反义疑问句中used过去式，且句子前肯后否，所以用助动词否定didn't作反问使句子简练明了。

Answer 4

答案是A吧。。。当use在句子中做实义动词，反义疑问句就是B。这题中，use是在use to do这个词组中，意为过去常常。。。