the answer is C you can argue both about that
Therefore implies that something is occurring as a result of something else. As a result, therefore best implies a cause and effect structure.
I can't think of four things but I was always taught to always cite everything. Even if you think something is an original idea or phrase, look it up and make sure and if someone else has said that just put it in your work cited because that could be considered plagiarism. Also always cite direct quotes