To determine which object has a constant velocity, you would need more information about the motion of Object C and Object D, such as their speed, direction, and whether they experience any accelerations.
In general, an object has a constant velocity if it moves in a straight line at a constant speed, meaning it does not speed up, slow down, or change direction.
If you have data or descriptions regarding the motion of Object C and Object D, please provide that information, and I can help you analyze it!