Oh my gosh, I love the Harry Potter series. But anyways, the central idea of this paragraph is that Harry should be getting some rest for the ongiong match and Mrs. Weasley will get Harry and the other's supplies.
The answer would be D. "I made just one request for the camping trip: I wanted to stay in a cabin instead of a tent."
Generally colons are used after phrases that are complete sentences. "I made just one request for the camping trip" is a complete sentence, and should therefore have a colon after it.