Select the most appropriate word to fill in the blank.
I would have forgotten my appointment if Susan _______ reminded me about it.

Options

A. hadn't
B. wouldn't
C. haven't
D. had

Explanation

hadn.t Rule: The verb in the “If clause” is in the past perfect tense, the verb in the Main clause is perfect conditional.
Sentence Structure: If + Past Perfect,
Subject would + have + Verb (`3^(rd)` form)