An object that has negative acceleration is definitely doing what?

speeding up

maintaining a constant speed

slowing down(incorrect)

accelerating in a direction that is opposite to a stated positive direction.

An object with 0 acceleration is accelerating in a direction that is opposite to a stated positive direction.

Explanation:

Acceleration is not always based on speeding up or slowing down (a constant speed is no acceleration at all), it's also based on direction. If you state that an object is positively accelerating when you throw it upwards, then it's negatively accelerating when it's falling even though it's velocity is increasing.

it is accelerating in a direction that is opposite to a stated positive direction

Explanation:

it's going backwards if positive is up then negative is down in ur case it's the opposite direction of forward

at right angles to each other