I started to collect postcards three years ago (对划线部分——three years ago 提问)

题目

I started to collect postcards three years ago (对划线部分——three years ago 提问)
完成上面的填空 _______ ________ you ________ to collect postcards?

答案

(When did) you ( start ) to collect postcards?
问时间用WHEN
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