He had studied English for a year before he came here 其中的before能不能换成when?
问题描述：
He had studied English for a year before he came here 其中的before能不能换成when?
答
不能.因为你前面用的是had studied,是一个完成时,
如果改成when的话,也就是是一个过去的时间点,那就要用过去时了.将had studied改成studied了.