Which of the following is not the additive inverse of a ?

⇒ Option A is the answer. Since, -(-a) is + a which is not the additive inverse of a.

⇒ Option B is not the answer as

⇒ a× (-1) = -a is the additive inverse of a

⇒ Option C is not the answer as –a is the additive inverse of a

⇒ Option D is not the answer as a÷ (-1) = -a is the additive inverse of a