Final answer:
The time it takes for a rock to reach the water when dropped from a cliff depends on the acceleration due to gravity.
Step-by-step explanation:
The time it takes for a rock to reach the water when dropped from a cliff depends on several factors. Wind speed, the rock's mass, and the rock's shape do not affect the time it takes. The only factor that affects the time is the acceleration due to gravity, which remains constant at approximately 9.8 m/s² near the Earth's surface.
Therefore, the correct answer is option c) Acceleration due to gravity.