This is about the order of events when a moving car hits a standing person. The very first contact is what forensic medicine calls the primary impact, and to locate it you simply ask which part of the vehicle reaches the body first. That part is the front bumper, and a bumper sits at roughly leg height for an upright adult. So the primary impact injury, the classic bumper fracture, lands on the legs, typically the lower leg around the level of the bumper. That makes option C the right choice. The trunk and head injuries come later in the sequence. Once struck low, the body rotates and is scooped up onto the bonnet, slamming the chest, abdomen and head against the car, and these are termed secondary impact injuries. A further set, the secondary injuries, occurs when the victim is finally flung onto the road surface. Because chest, abdomen and head all belong to those later phases, they cannot be the primary impact site. The bumper-to-leg contact is what defines the answer. $C$ is correct. \[\boxed{\text{Legs}}\]