What is the primary role of the gear lever in a manual transmission?

The primary role of the gear lever in a manual transmission is to shift gears based on driver input. This control mechanism allows the driver to select the appropriate gear for their desired speed and driving conditions. By moving the gear lever through its various positions, the driver engages different gears, which consequently changes the torque and power delivered from the engine to the wheels. This direct interaction gives the driver the flexibility to optimize the vehicle's performance, whether accelerating, climbing hills, or saving fuel.

Other options refer to functions not related to the gear lever's purpose. For example, controlling vehicle speed is accomplished through both throttle input and gear selection but is not directly managed by the gear lever itself. Fuel injection is handled by the engine's electronic control unit, and regulating engine temperature is typically managed by the cooling system, making them unrelated to the function of the gear lever in shifting gears.