The correct answer is - C. Determine which author used the most reliable sources.
This is extremely important when trying to find out the truth and to determine what is right, what is wrong, what is a subjective opinion, or what is objective opinion. By using the most reliable sources, the author proves that he/she is trying to portray the real picture of what happened, and not expressing theories or personal opinions about things he/she has not witnessed, or to be influenced by only one side of the war.