If a source is reasonable, we know letter C: the information offered is fair, balanced, easy to believe, and consistent. Reasonable, meaning people will understand its simple implications.
If it is letter A: the information offered is up-to-date, factual, detailed, and precise., then the information is factual or reliable.
If it is b: the information is universally accepted. The information is general.
If it is d: we can trust and believe the author. The information is general from an expert or with authority.