When driving a light vehicle down a steep hill, what is the risk of keeping the clutch pedal fully depressed (declutched) for the entire descent?

1. The vehicle will accelerate rapidly due to gravity, and the brakes may overheat and fail
2. The clutch release bearing will fuse with the engine crankshaft
3. The transmission gears will automatically shift into reverse
4. The engine will run out of fuel because the fuel pump stops