Which one of the following is considered part of the cowl?

The cowl is an essential part of a vehicle's structure, positioned between the windshield and the engine compartment. It serves multiple purposes, such as supporting the windshield and accommodating various components like ventilation and drainage systems. The vent panel, which is often part of the cowl area, specifically plays a crucial role in directing airflow into the cabin and aiding in ventilation.

The other options listed do not constitute part of the cowl. The quarter panel is primarily the section of the vehicle at the back and side, often associated with the rear wheel area. The grille is located at the front of the car and is designed to allow air to flow into the engine compartment for cooling purposes. The fender, on the other hand, is situated over the wheel wells, protecting both the vehicle and pedestrians from debris and is not connected to the cowl area directly. Therefore, the vent panel stands out as the correct choice, as it is a distinct feature of the cowl, directly involved in the vehicle's airflow systems.