Final answer:
Drivers should be ready to shift to a lower gear when they see this sign. Option C is correct.
Step-by-step explanation:
This sign indicates a steep downhill grade. Drivers should be prepared to shift to a lower gear to maintain control of their vehicle and avoid losing brake effectiveness due to excessive speed. This is especially important for heavy vehicles and trailers, as they are more susceptible to braking problems on steep downgrades.
Option A, braking sharply and stopping, is not the appropriate response to this sign. While it is important to be aware of your surroundings and ready to react to potential hazards, slamming on the brakes can be dangerous and lead to loss of control. Instead, drivers should gradually reduce their speed by downshifting and using the engine's braking power.
Option B, yielding to trucks coming from the hill on the right, is not always necessary. Drivers should always be cautious and yield to vehicles in their blind spots, but this sign does not specifically indicate that there is a risk of overtaking trucks. The primary focus should be on downshifting to maintain control.
Therefore, the correct answer remains C: be ready to shift to a lower gear.