Choose the correct singular, third person, conjugation of the verb to be in the future perfect tense.
a. she will have been
b. you have been
c. they will have been
d. i will be

Third person singular is he/she/it.
Having this in mind, the correct answer is A. She will have been.
You is second person singular/plural, they is third person plural, I is first person singular. 

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