一、during which的用法：

during which相當於during the time / the period / the course of …，既可用於限制性定語從句也可用於非限制性定語從句；可指時間，也可指過程或階段等。意為“在……期間；在……過程中；在……階段”等。

1. during which 用於限制性定語從句時，脩飾對象為先行詞，先行詞在定語從句中表“在……期間；在……過程中”。如：

September and October are the months of the year during which most English people take their holidays. 一年中9、10兩個月是大多數英華人休假的月份。

說明：句中的during which = and during the time of the months of the year表“一年中的這兩個月間”。

In 1988, Vietnam and china fought a brief naval battle during which more than 70 Vietnamese sailors died. 1988年，越南和中國曾進行過一次小規模海戰，70多名越南士兵在戰鬥中喪生。

說明：句中的during which = and during the course of the brief naval battle 表“小規模海戰期間”。

2. during which 用於非限制性定語從句時，不脩飾整個句子，只修飾句子中的某個詞（組），被脩飾的詞（組），在從句中表“在……期間；在……過程中”。如：

She kept her vow for a week, during which she was unusually cross and fretful. 她信守誓言有一星期之久，但在這一星期內，她顯得五心煩躁，動不動就發脾氣。

說明：句中的during which = and during the time of the week 表“在這一星期期間”。

He died in the Anti-Japanese War, during which my grandfather fought side by side with him. 他在抗日戰爭中為國捐軀，在抗戰期間，我祖父曾與他並肩戰鬥過。

說明：句中的during which = and during the period of the Anti-Japanese War表“在抗日戰爭期間”。