When I___in primary school,I___to play the piano. A.was,learnt B.am,learnt C.was,was learning

题目

When I___in primary school,I___to play the piano. A.was,learnt B.am,learnt C.was,was learning
D.am,am learning原因?

答案

When I was in primary school,I learnt to play the piano.
A
两个过去时
我小学时,学会了弹钢琴.