Which of the following vehicles only may carry a red light visible from the front?

Answer: D — Emergency vehicle responding to a call

Emergency vehicles responding to a call are the only vehicles allowed to carry a red light visible from the front. Both commercial motor vehicles and pleasure type motor vehicles do not have this privilege. Additionally, bicycles are not allowed to carry any type of colored lights on the front. They are only allowed to have a white light visible from the front. Therefore, the only correct option is D, emergency vehicles responding to a call.