The answer would be the first choice or A. "Original ideas that are <em>not</em> your own."
Any piece of information that does not belong to you would require a citation, otherwise it would be considered <em>plagiarism. </em>B and C are incorrect because both of those things belong to you, and therefore don't require citation. D is also incorrect because a general fact doesn't belong to any one person. For example, if you wanted to include the information that dogs can't eat chocolate, that wouldn't require a citation because that is general knowledge that most people are aware of.
The outcome of a poorly written subject line would be that the reader wouldn't understand what he/she was reading about. This would in turn, keep the reader confused the rest of the literature and wouldn't be able to focus.
Dear Yale,
Can you please give me a tour of the school. Can you tell me the classes, you are teaching.