Since we don't know the sign of the acceleration, it's not answerable...other than either C or D; however, since (de)acceleration can be used to mean positive (negative) acceleration, D looks correct to me.

Since we don't know the sign of the acceleration, it's not answerable...other than either C or D; however, since (de)acceleration can be used to mean positive (negative) acceleration, D looks correct to me.

Edit: Note that the phrase "can be used to mean" is synonymous with common English and/or "strongly suggests", but this is a physics problem, and we all know physics and language don't always mix.