Iknow that the pe will be the same for all the objects, but other then that i'm confused on what is correct and what isn't.

Neither aspects of Dominique are correct.

Explanation:

They will not have the same speed before hitting the ground.

The block C has an initial horizontal velocity v₀ₓ , therefore the total ultimate speed before hitting the ground is  v = √ v₀ₓ² + vy²

It didn't matter how the blocks were dropped, they all landed at the same time. If any block has an initial vertical velocity it will have a higher end velocity. If Dominique means dropped from the rest then the previous claim is true. It is important how they were dropped.

The Dominique must said : The vertical speed will be the same because of conservation of energy.

The fact is,  they all landed at the same time and that is true. And it is important how they are thrown away.

God is with you!!!

the chart show the masses and velocities of two colliding objects that stick together after a collision.

according to the law of conservation of momentum, the momentum of the object after the collision is  

answer

1,500

kg • m/s.