Is answer C saying that it's a premise but in a much more fancier way?

Hi Tyler808, C is actually describing an intermediary conclusion. If support is provided for a statement, then that statement is a type of conclusion, however if it is also used to support another statement, then the initial statement is an intermediary conclusion. For example, we could say X, therefore Y, Therefore Z. X is a premise, Y is an intermediary conclusion, and Z is the overall conclusion.