A

would表示过去的习惯性动作, would 后跟行为动词，不跟表示状态的动词，往往有时间状语，而used to表示过去的习惯动作时后跟的动词无限制，无需有时间状语，如：

I used to like chocolate.        (√)

When I was a child, I would like chocolate.        (×)

I used to be a university student.          (√)

I would be a university student.           (×)