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同学你好~
介词的位置在which的前面。介词通常和动词有关系，比如
This is the house in which we lived last year. 这是我们去年居住的房子。
这个句子相当于This is the house which we lived in last year.
which指代的是house，实际上which we lived in中which是in的宾语，这种情况下可以把in提前到which前，变成in which we lived
Copper is one of the metals with which we are most familiar.铜是我们最熟悉的金属之一。（形容词familiar与with连用）
Please tell me from whom you borrowed the English novel. 请告诉我你从谁那借的这本英文小说。（动词borrowed和from连用）

有的时候介词还可以和关系代词构成词组，比如
It is the sixth month in a row in which imports have fallen.
这是进口量持续下降的第6个月了。
which指代the sixth month，in which相当于in the sixth month

祝同学学习进步~