It was in Germany ____ Einstein spent his childhood。A。where B which C that Dwhen想问A是不可以的，答案是C，但是B为什么不可以。还有一道：She is the girl ____helped us a lot .这里是不是Who that 都能用有没有通俗易懂的判断应该用who /that /which的方法？拜托，有人告诉我我一定给高分。