Which situation is most likely to cause stalling in a manual vehicle?

Releasing the clutch too quickly without giving the engine enough throttle is the situation most likely to cause stalling in a manual vehicle. When you release the clutch rapidly, the engine may not be able to maintain enough power to keep running, especially if the vehicle is in a gear. This abrupt disengagement can lead to a significant drop in engine RPM, causing it to stall because there is not enough momentum to keep the engine turning over.

The other scenarios do not lead to stalling when performed correctly. Fully pressing the gas pedal typically increases engine RPM, providing more power rather than stalling. Gradually releasing the handbrake is a necessary part of starting to move the vehicle, and with proper throttle use, it should not cause stalling. Engaging the clutch smoothly allows for a gradual transfer of power from the engine to the wheels, which helps maintain engine RPM and avoid stalling. Thus, the risk of stalling is heightened when the clutch is disengaged too quickly without adequate acceleration.