A few English words have such disparate definitions that one meaning is the opposite of another. These are called "self-antonyms", "auto-antonyms" or "contronyms". Which of the below given words are "SELF-ANTONYMS". One example is "overlook" (to view over or to fail to notice)

'Fast' is indeed a contronym (self-antonym) because it has opposite meanings: 1) moving quickly (rapid, swift) and 2) fixed or immovable (stuck, fastened, hold fast). The other options don't have this contradictory property: 'fats' is just a plural noun, 'stop' means only to cease movement, and 'post' can mean to mail or a pole but these aren't true opposites. The example 'overlook' works similarly: to oversee/watch over vs. to fail to notice.