A research paper goes beyond a summary, a review or a collection of information. It is a representation of the writer's point of view based and forged by experts' information, that are quoted and cited to support it, bringing evidences of his personal interpretation on the subject.
Although it is the writer's point of view, it must not sound personal. Also, the quotations the writer brings along cannot be 'general' for it will not help him support his point of view, but it has to be precise and very well connected with the subject, as statistics (Letter A) always are and always represent best many information, making it the correct answer.