The gearbox helps transmit , change the torque and cut off the transmission from the engine to the active wheel + ensures the car to move in reverse.
Answers 1 and 2 are wrong because there is no drive cutoff + reverse motion
Transmit and increase torque between perpendicular axes, ensuring that the active wheels rotate at different speeds when the resistance to movement on the two wheels is not equal.
Transmission and change of torque between axes that are not on the same line, and the misalignment angle always changes during the car's motion, smooth shifting, easy to control.
Transmit and change the torque from the engine to the active wheel, cut off the transmission from the engine to the active wheel, ensuring the car to move backwards