Concept: The subject "one" is singular, so the verb must agree with it.Explanation: The sentence is: "One of his close friends ___ a soldier." The subject is "one", not "friends". Since "one" is singular, we need a singular verb in the present tense. The correct word is "is". Options "are", "have been", and "were" are plural and do not agree with the singular subject.Answer: A. is