I was taken aback on the correct format for the following tense:
Present Perfect: I have sat
Past Perfect: I had sit
Future Perfect: I SHALL HAVE SAT?!

Please tell me what is the correct structure for the above??

Thank you!
I am afraid we need a "CONTEXT". The past perfect is wrong.
Present Perfect : Whenever an action is completed with no time mentioned.

eg. I have finished my jobEmotion: smile

Past Perfect : Two actions that took place in the past with one earlier than the other.

eg. When I came in, he had left EnglishForwardEmotion: smile

Future Perfect : A fixed time to have something done.

eg. We shall have completed this project by next month.Emotion: smile
Students: We have free audio pronunciation exercises.
i hope this is right. i am taking my Lang. Arts Praxis II test saturday, and i am refreshing mt tense usage. this is the only place i could find that gave an exact def. of prefect tenses!
Ask any (precise) question you have, Anon. We'll do our best to answer as quickly as possible!
I have sit.

I had sit.

I will have sit.
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I have sit sat.

I had sit sat.

I will have sit sat.