If cooling air passes over intake air, this is known as what type of aftercooler?

The correct answer identifies a configuration known as an Air-to-Air aftercooler. In this setup, cooling air flows over the intake air to reduce its temperature before it enters the engine or turbocharger. This method effectively increases the density of the intake air, allowing for better combustion efficiency and enhanced engine performance. Utilizing ambient air as a cooling source, the Air-to-Air aftercooler relies on heat exchange between the two air streams to achieve optimal cooling without the need for additional fluids, making it a preferred choice in many applications.

The other options represent different configurations that use other mediums for cooling, but they do not specifically describe the process where cooling air is used to lower the temperature of intake air directly. Each of those alternatives involves different types of coolants or media that serve distinct purposes in thermal management of engine components.