What does “stalling” indicate in relation to a manual vehicle?

Stalling in a manual vehicle refers to the engine stopping unexpectedly, typically due to insufficient throttle input or improper handling of the clutch. When the driver doesn't provide enough power to the engine (throttle) while engaging the clutch, particularly in situations where more power is needed—such as during take-off or on an incline—the engine may struggle and ultimately stop running. This loss of power results in the engine halting, which is what is meant by stalling.

In contrast, the other options do not align with the definition of stalling. An engine that is idling properly suggests that it is running smoothly and not experiencing issues, while being in motion at high speed might imply the engine is functioning adequately. Lastly, a transmission in perfect working order would not typically cause stalling; rather, it should facilitate smooth gear changes and power transfer from the engine to the drivetrain. Thus, the correct answer captures the essence of what happens to the engine during a stall event in a manual vehicle.