Using Which with Prepositions

 "Which" can be used after a preposition, especially in more formal writing.

• Example: "There are several small ponds in which a variety of fish live."
• Less formal alternative: "There are several small ponds which a variety of fish live in."
• Example: "This is the quotation to which I was referring."
• Less formal alternative: "This is the quotation which I was referring to."