What must service brakes be adequate for?

The correct answer focuses on the necessity for service brakes to effectively control the movement of the vehicle and bring it to a stop under all loading conditions. This means that the brakes must perform reliably whether the vehicle is empty or fully loaded, ensuring safety and control regardless of the circumstances.

Brakes that only stop the vehicle may not account for different conditions, such as heavy loads or downhill slopes, where more braking force is required. They must be able to manage the momentum created by varying weights and different driving scenarios, guaranteeing that the vehicle can consistently operate safely.

While some options hint at specific scenarios, such as emergency situations or tire wear, those do not encompass the primary function of brakes in general operation and safety. This broader understanding reinforces the critical role of service brakes in vehicle safety and control.