Why the dam of water reservoir is thick at the bottom.A Quantity of water increase with depth. B Density of water increases with depth. C Pressure of water increases with depth. D Temperature of water increase depth.

The dam of a water reservoir is thicker at the bottom due to option C: Pressure of water increases with depth.

Here's the step by step explanation:

1. Water pressure increases with depth: This is due to the weight of the water above pushing down on the water below. The deeper you go under the surface of the water, the greater the pressure of the water above you.

2. The increased pressure at greater depths pushes against the dam: The water pressure at the bottom of the reservoir is greater than at the top because it has the weight of all the water above pushing down on it.

3. The dam needs to be thicker at the bottom to withstand this greater pressure: If the dam was not thicker at the bottom, it could fail under the greater water pressure. The thickness of the dam increases its strength and ability to withstand the pressure of the water.

So, the dam of a water reservoir is thicker at the bottom primarily due to the increased water pressure at greater depths.