I am sorry I have just seen the past discussion post on this exact question.
Emil-Kunkinon April 19, 2022
Hi Cameron,
Just adding this in in case anyone stumbles across this in the future. Answer choice C is too narrow, the main purpose of the passage is to answer various critics of the oath, not just to note that historical doubts are unimportant. Those doubts were just one line of attack against the oath.