關於Absented的意思和用法的提問

A: The correct one is "If I had been absent, ....".

"If I had absent" and "If I had absented" are not correct, because when we use this tense 'had' must be followed by the past participle of a verb (in this example 'been').
"If I had been absented" is not correct, because in this context, 'absent' is an adjective, and we don't conjugate adjectives.

This is a difficult tense to learn in English, it is used to describe an event that began and finished in the past. The usual form is "had been" + an adjective or another verb with 'ing'.
"If I had been happy, I would have done a better job."
"If I had been sleeping, I wouldn't have heard it."

I hope this isn't too confusing!

A: He has been absent for three days.