To determine which object has a constant velocity, we would need information about the motion or the position-time graph of Object C and Object D.
- If the position of an object changes at equal intervals of time in straight line motion, that object is said to have a constant velocity.
- If the object's position is changing at varying rates or direction, then it does not have a constant velocity.
Without any data or context regarding the motion of Objects C and D, I cannot definitively determine which has a constant velocity. Please provide more details about their movements or states.