有關"in which"及"，in which"的問題!!

你好~
請看以下例句：

In my laboratory there is a blue cabinet in which old equipment is stored.
原句為：In my laboratory there is a blue cabinet which old equipment is stored in.

A man can succeed at almost anything for which he has unlimited enthusiasm.
原句為：A man can succeed at almost anything which he has unlimited enthusiasm for .

It is the spirit with which you endow your work that makes it useful or futile.
原句為：It is the spirit which you endow your work with that makes it useful or futile.

在這裡 "which" 是「關係代名詞」，英文文法的規則是若關係代名詞子句裡有「介繫詞」，它們就得移到關係代名詞的前面。這已經成為一個慣用法，把介繫詞和關係代名詞分開幾乎是沒看過人用了… 所以就你問題中的 4 句話，我把它們還原如下 (粗體字為先行詞)：

1. They are formal events which teens share their traumatic experiences in.

2. The word "prom" was first used in the 1890s, referring to formal dances which the guests of a party would display their fashions and dancing skills in during the evening's grand march.

3. These programs require weekly meetings between students and their homeroom teachers, which students are free to openly discuss any issues they might be confronting at school in.

4. This represents a big change from decades past, which bullying was just seen as a part of attending school in.

然而，如上所說的，現在只要關係代名詞子句裡有介繫詞，它們就得移到關係代名詞前面。這已經是英文的慣用法，外國人已不會去想說介繫詞原本該放哪，而是下意識的直接把合適的介繫詞加進去。至於逗號的用法，它是要讓很長的句子可以停頓一下。補充說明：in which 可以用 where 來替換，以上所有的例句皆可以。

請參考：
http://www.dailyenglishquote.com/2010/05/adelaide-hasse/
http://www.dailyenglishquote.com/2010/09/winston-churchill-3/
http://www.dailyenglishquote.com/2011/03/erica-jong/

2012-01-13 22:03:08 補充：
回你的問題：

「還是，因為先行詞有了，而所以省略了本來要在in後面接的先行詞呢」

沒錯，正是如此！

1. which 是指 formal events.
They are formal events. Teens share their traumatic experiences in these events.
兩句合起來便成為
They are formal events in which teens share their traumatic experiences.

2. formal dances 意思是舞會
in which 就是 in the dances

The word "prom" was first used in the 1890s, referring to formal dances. In the dances (party) the guests of a party would display their fashions and dancing skills during the evening's grand march.

兩句合起來便成為
The word "prom" was first used in the 1890s, referring to formal dances in which the guests of a party would display their fashions and dancing skills during the evening's grand march.

1, 2 兩句將 in which 改為 where 意思就很容易明白了。

3. in which 指 in the weekly meetings. 第三句的 "，" 只因 which 跟 weekly meetings 相隔甚遠，加上 comma 令句子容易明白。

4. which 指 decades past, in which 就是 in those days 的意思。 in which 也可以用 when 代替。
第四句的 "，" 可以省去。
The (something?) represents a big change from decades past. In those days bullying was just seen as a part of attending school.

2012-01-07 01:05:11 補充：
您是如何判定第一句的in，後面要接these events.呢?

不單是第一句，找出 in which 的 which 所指只須從 which 字向前看，which 前的第一個名詞或名詞片語，絶大多數就是 which 所代表的物件。
1. formal events
2. formal dances
3. 不可能是 students 或 teachers，weekly metings
4. decades past

2012-01-07 01:08:33 補充：
第四句 which 是代表 decades past。in those days 只是另一個寫法而矣。

2012-01-07 01:20:52 補充：
John 回答者002 的解釋很詳盡，還有一點我想補充。
which 不錯是「關係代名詞」，它是代表之前曾經提及的名詞，但當 in which 放在一起時，in which 用作 where (地方、事件) 或 when (時間)，where 或 when 可取代 in which，in which 的詞性屬於連接詞(conjunction)而非代名詞。

2012-01-07 01:28:38 補充：
您(John)所還原的那四句句子，in後面不用再接名詞(或地方名詞)了嗎?

不用。其實就好像下句一樣
This is the ring which I gave Mary yesterday.
Mary 後不用 the ring 因為 which 已經是指 the ring。

John 的四句還原句in後面不用再接名詞(或地方名詞)因為在前面的 which 已經指出了。

***Teens share their traumatic experiences in the formal events.



***---bullying was just seen as a part of attending school in the past decades---


意見欄無法用顏色 還有 你那個第四句還是錯的呀 中間兩句太長了 意見欄只能塞 300 字

第四句打漏字了，the不能當句子的主詞。請檢查一下全句。