On a narrow mountain road without a central divider where two vehicles meet from opposite directions, which vehicle has the right-of-way?

1. The vehicle on the mountain side (靠山体的一方) has priority
2. The vehicle on the cliff/precipice side (不靠山体/靠悬崖的一方) has priority; the mountain-side vehicle must yield (靠山体的一方让不靠山体的一方先行)
3. The vehicle traveling at higher speed has priority
4. The heavier commercial vehicle always forces the smaller car to reverse