If you are driving down a steep downgrade, you should

Answer: D — Shift into a lower gear

When driving down a steep downgrade, shifting into a lower gear helps to control your vehicle's speed and reduce the strain on your brakes. This is because a lower gear provides more resistance and helps to slow down your vehicle without applying excessive pressure on the brakes. Shifting into a higher gear or keeping the vehicle in neutral will not help control your speed and can put stress on your engine. Applying the brakes firmly can also cause wear and tear on your brakes and may result in overheating, which could lead to brake failure. Therefore, shifting into a lower gear is the safest and most efficient option when driving down a steep downgrade.