C is the best answer. A is close to being correct, but C is the most well-spoken answer. You can eliminate choice D because they have spelled "which" incorrectly, writing it as "witch". A is not the best answer because "them" refers to people, and a room is a thing, not a person. We use "which" in English to distinguish between two possible options, so here it is the correct choice.

After giving it some thought... yeah, that makes sense, thanks for clarifying man. :D!!

D. the smaller of WHICH Sorry that's my typo, my apologies ....

Them is not used only to refer to people. That is incorrect. "Smallest" should only be used to refer to one of a group of MORE than two objects. When comparing only two objects, "smaller" is the proper term. If which is spelled correctly, C is the only proper choice. The reason A is inferior is because it is a complete sentence, It cannot be joined to another complete sentence with a comma. It needs either the word "and" after the comma or it needs to be joined with a semicolon ; instead of a comma.

A.