A linking verbs link the subject to a word or phrase, it tells us more about the subject, in this context, the main subject is Mexico, so "feels" links with the adjective and rest of the phrase to convey meaning. On the other hand, decided cannot be possible as it is the only verb used to tell about "I" not Mexico; air is a noun and hot is an adjective.
The answer is c, feels. the reason why is because a verb is a word that describes the feeling, that of, the verb in this sentence being "comfortable" the word feels is linking the verb to this sentence, its announcing it.
