譬如:
Her book,“Determined,Dedicated and Disciplined To Be Fit,”came out in April just before she turned eighty.
The bus had left before I arrived.
为何两个不同呢?什么时间用一般过去时,什么时间用过去完成时。
before引导时间状语从句,主句用一般过去时或过去完成时均可。
与此有关的更多内容可参考我以前的一个解答:http://ask.yygrammar.com/q-27705.html