---(1) the train (2)(leave) yet?

问题描述:

---(1) the train (2)(leave) yet?
---yes,it(3)(leave)half an hour ago.
第(1)填Has 第(2)填left
那第3个为什么要填left而不能填has left呢?

an hour ago
有确切的时间点,用过去式