When you park on an uphill grade, a driver should:

A. Turn the vehicle's wheels to the left and slowly let the car roll back until the right front wheel rests against the curb and stops, then set the parking brake.
B. Turn the vehicle's wheels to the right and slowly let the car roll back until the left rear wheel rests against the curb and stops, then set the parking brake.
C. Turn the vehicle's wheels to the right and let the car roll forward until the left rear wheel rests against the curb and stops, then set the parking brake.
D. Turn the vehicle's wheels straight and engage the parking brake.

When you park on an uphill grade with a curb, the correct action to ensure your vehicle's safety is to: Turn the vehicle's wheels to the left and slowly let the car roll back until the right front wheel rests against the curb and stops, then set the parking brake.

This method ensures that if your vehicle starts to roll, it will roll into the curb and stop, rather than rolling into traffic. It's crucial to set the parking brake securely to prevent the vehicle from rolling away.

Remember, the aim of turning the wheels is to use the curb as a stopper if your parking brake fails. Parking techniques can vary depending on whether you're facing uphill, downhill, or if there's no curb. Always practice safe parking habits to avoid accidents and ensure the safety of everyone around.