"on which" 和 "in which" 都是介词短语,但它们用法上有些不同。
"on which" 表示某物或某人所处的位置或状态。例如:
The book on which I am reading is very interesting.(我正在读的书很有趣。)
The table on which the vase is standing is made of oak.(花瓶所放的桌子是橡木制的。)
"in which" 则表示某物或某人所处的位置或环境。例如:
The house in which he lives is very old.(他住的房子很老。)
The city in which I was born is located in the northeast.(我出生的城市位于东北部。)
总的来说,"on which" 更强调所处的具体位置,"in which" 则更强调所处的环境或位置。