What happens when the throttle is advanced (opened)?

When the throttle is advanced or opened in an internal combustion engine, it allows more air to enter the intake manifold. This increased airflow is crucial because it requires a corresponding increase in fuel to maintain the proper air-fuel ratio for combustion. As a result, more fuel is drawn into the carburetor or injected through the fuel injectors to match the increased volume of air entering the engine. This additional fuel is necessary to ensure that the engine can produce more power and respond effectively to the driver's demands, such as accelerating the vehicle.

In contrast, the other choices describe processes that do not occur when the throttle is opened. Cooling in the radiator is managed by the cooling system and is unrelated to throttle position. Reducing the amount of fuel drawn into the fuel injectors would hinder the engine's performance instead of enhancing it. Lastly, mixing air with oil for lubrication is a function related to the engine’s lubrication system, not the throttle mechanism, which is specifically concerned with regulating airflow into the engine for combustion purposes. Thus, option C accurately reflects the effects of advancing the throttle.