which的用法
which是一個引導非限制性定語從句的代詞，用于指示先行詞。在定語從句中，which通常放在先行詞之后，并且用來修飾先行詞。
which用法詳解
1. which one(s)：指代先行詞中的一個或多個。例如：I want to buy which one(s) of the books.
2. which case(s)：指代先行詞的某一特定情況或狀態。例如：In which case(s) did you speak to the teacher?
3. which of：指代先行詞中的幾個中的一個。例如：The table is which of the ones we had in the living room.
4. which they(re)：指代代先行詞的復數形式。例如：The children are which they(re) of the two who are studying abroad.
5. which one(s) to：指代在從句中用來引導非限制性定語從句的哪一個或哪些。例如：Which one(s) to buy, we should consider the prices.
6. which they(ll)：指代在從句中用來引導限制性定語從句的哪一個或哪些。例如：Which they(ll) buy, we should consider the prices.
which用法總結
which引導定語從句時，其用法因語境而異。一般來說，which one(s)、which case(s)、which they(re)和which they(ll)的用法比較常見，需要根據具體語境來選擇合適的用法。同時，在定語從句中，which的位置也很重要，需要根據先行詞在句子中的語境來選擇合適的位置。
