Choose the correct singular, third person, conjugation of the verb to be in the future perfect tense.

A. You have been
B. I will be
C. She will have been
D. They will have been

is it D?

No. That's in the future perfect, but it is not singular.

So it's A?

singular = one person or thing

third person = not I, you, or we
future perfect = has "will have" for helping verbs

In D, "they" is plural. Which sentence has the singular third person?

Yes, the correct answer is D. "They will have been" is the correct singular, third person, conjugation of the verb to be in the future perfect tense.

To arrive at this answer, let's break it down:

The future perfect tense is used to describe an action that will be completed before a specific time in the future. It is formed by using "will have" followed by the past participle of the verb.

In this case, the verb is "to be." The base form of "to be" is "be," the past participle is "been."

To conjugate the verb "to be" in the third person singular form, we use "will have been."

A. "You have been" is in the present perfect tense, not future perfect tense.
B. "I will be" is in the future tense, not future perfect tense.
C. "She will have been" is in the future perfect tense, but it is not singular, third person.

Therefore, D is the correct answer: "They will have been."