是from which吧??
主要是用在定语从句中,which作为先行词,指代前面已经提到的某物或某事情,例如:
I have just taken part in ShangHai car exhibition, from which I learned the advanced technology of car manufacturing.
我刚刚参加了上海车展,从中学习到了很多先进的汽车制造技术。
这句子里面的"which"指代"ShangHai car exhibition",之所以要在"which"前面加"from",是因为"learn"在此处做不及物动词,"learn from"作为短语可以理解为"从.....中学到"!
小生才疏学前,希望大家拍砖!!