Answer:
D
Explanation:
A compound subject is a subject made up of two or more simple subjects that are joined by a coordinating conjunction and have the same predicate.
Verb = doing word/word that represents action
Predicate = state, affirm or assert something about the subject of a sentence.
Subject = person, place, thing etc. in a sentence.
Conjunction = used to connect words, phrases, clauses or sentences.
Coordinating conjunction = conjunction placed between words, phrases, clauses and sentences of equal rank eg. and/but/or.
In this case fans and air conditioner are subjects and even though they are both singular, now that they are joined by the word "and", they are now part of a plural structure. as a result the plural verb "are" has to be used in this sentence.