The correct option is A improvement
The word 'deterioration' refers to the process of becoming progressively worse.
Option A, reformations refers to the process of restructuring an action or place.
Option B, amendment refers to an alteration or addition to improve something.
Option C, improvement refers to a thing that makes something better.
Option D, revision refers to the action of revising and reworking.
Thus, according to the meaning, the word 'improvement' is the opposite of the word 'deterioration'.