The correct answer is A. has.
Merry is a singular subject, so it takes a singular verb. The verb “has” is the present tense form of the verb “to have,” which is used to indicate that someone or something possesses something. In this case, Merry possesses two husbands.
The other options are incorrect because they are either plural verbs or do not agree with the subject of the sentence. The verb “have” is a plural verb, so it cannot be used with a singular subject. The verb “is” is a singular verb, but it is used to indicate that someone or something is a particular thing. In this case, Merry is not a particular thing; she is a person. The verb “are” is a plural verb, and it is used to indicate that two or more people or things are doing something together. In this case, Merry is not doing something together with two or more people; she is simply possessing two husbands.