"First off, the extreme word exclusively is a big warning sign that this answer is probably wrong, so you should be suspicious of"

"First off, the extreme word exclusively is a big warning sign that this answer is probably wrong, so you should be suspicious of" it from start.

Explanation:

"First off, the extreme word exclusively is a big warning sign that this answer is probably wrong, so you should be suspicious of" it from start. The author writes about power sellers at Ebay. Those power sellers started using Ebay as regular users but over a period of time they turned out to be the power sellers and the author mentions these power sellers in the passage.

i think it may be b, i'm not exactly too sure on this. but b seems to make more sense.