The correct answer is A) starting air and fuel pumps. To reverse the rotation of a two-stroke cycle loop scavenged, direct reversing, propulsion diesel engine, the cam positions for the starting air and fuel pumps must be changed. This is because the starting air and fuel pumps are responsible for supplying the necessary air and fuel to the engine, and their timing must be adjusted to accommodate the reversed engine rotation. The other options (B, C, and D) are incorrect because changing the piston cooling pumps or exhaust valves alone would not be sufficient to reverse the engine's rotation. The starting air and fuel pumps are the critical components that need to be modified to achieve the desired engine rotation reversal.