这两个词的区别我懂，给大家做一个简单的表格，先大概的了解一下~~
"in which"、"on which" 和 "at which" 都是英语中常见的短语，用来表示某个事件或事物所处的位置或环境。以下是它们之间的五个主要区别：
1. 含义：
"in which" 表示某个事件或事物所处的环境，常用于描述某个场所或物品所在的情况。
例子：The room in which the meeting was held was quite small.
中文翻译：会议所在的房间非常小。
"on which" 表示某个事件或事物所处的位置，常用于描述某个物体的位置。
例子：The plate on which the cake was served was made of porcelain.
中文翻译：蛋糕放在瓷盘上。
"at which" 表示某个事件或事物所处的位置或环境，常用于描述某个场所或物品所在的情况。
例子：The restaurant at which we ate last night was very expensive.
中文翻译：我们昨晚吃饭的餐厅非常贵。
2. 语法：
"in which" 通常作为一个关系副词，用于修饰一个从句。
例子：The hotel in which we stayed was very comfortable.
中文翻译：我们住的酒店非常舒适。
"on which" 和 "at which" 则通常作为一个介词短语，用于修饰名词。
例子：The table on which the book was placed was very old.
中文翻译：书放在的桌子非常旧。
3. 使用场合：
"in which" 常用于书面语，尤其是学术论文或正式文献中。
例子：The research project, in which we investigated the effects of climate change on crop yields, was funded by the government.
中文翻译：我们调查气候变化对作物产量的影响的研究项目得到了政府的资助。
"on which" 和 "at which" 则更常用于日常口语或非正式文本中。
例子：The chair on which I usually sit is broken.
中文翻译：我平时坐的椅子坏了。
4. 表示的时间：
"in which"、"on which" 和 "at which" 也可以用于表示特定的时间，但它们的使用情况和含义有所不同。
例子：The day on which she arrived was a Friday.
中文翻译：她到达的那天是星期五。
例子：The month in which the conference is being held is September.
中文翻译：会议举办的月份是九月。
例子：The time at which the concert starts is 7 PM.
中文翻译：音乐会开始的时间是晚上七点。
5. 代替：
"in which"、"on which" 和 "at which" 还可以用来代替某个名词或名词短语，以避免重复使用。在这种情况下，它们通常被用作关系代词。
例子：The university, at which I studied, has a very good reputation.
中文翻译：我就读的大学声誉很好。
例子：The book, in which I found the information, was very interesting.
中文翻译：我在这本书里找到了这个信息，这本书非常有趣。
例子：The house, on which we put a new roof last summer, looks much better now.
中文翻译：我们去年夏天为这座房子换了新屋顶，现在看起来好多了。
总之，虽然 "in which"、"on which" 和 "at which" 的意义相似，但它们在语法、用法和含义上都存在细微的差异。在实际应用中，需要根据具体语境和需要来选择正确的短语。