You are in your car towing a trailer which has no brakes and you approach a long steep downhill slope. What is correct?

Your answer is fully correct. When towing a trailer without brakes on a long, steep downhill slope, you must reduce speed and, if needed, shift to a low gear early to use engine braking. This helps control your speed without overusing the brakes and risking overheating. Additionally, you need to be aware of the trailer's pushing effect, meaning it pushes against your car, increasing the force you need to control. Relieving the brakes by disengaging the clutch is incorrect because it reduces braking effectiveness and can be dangerous. So, careful speed control and anticipating the trailer's behavior are essential for safety.