Chose the correct singular third person conjugation of the verb to be in the future present tense

A - I will be

B-you have been

C - they will have been

D-she will have been

It seems that you have an error on the question.

The right question must be choose the correct singular third person conjugation of the verb to be in the future perfect tense not future present tense.

Answer: option D. she will have been.

The future perfect tense is the tense that indicates that the action will have been completed in the future.

The future perfect tense is formed with "will" plus "have" plus the past participle of the verb.

In this case, she is the singular third person pronoun.

And been is the past participle of the verb to be.

So, the pronoun + "will" + "have" + past participle is she will have been.