Part A How do the potential energy and the kinetic energy change when the skateboarder is at the top or the bottom of the hill? Why do you think this change occurs?

The potential energy (P.E) and the kinetic energy (K.E) are two types of distinct energy that is commonly observed in our day-today's life.

Usually, K.E is defined as a type of energy that is produced when an object is in motion. Where, as P.E is a type of energy that is stored in an object when that object is placed at a certain height.  

In the given condition, when the skateboarder is at the top of the hill, then at that position, it is comprised of maximum P.E. As the he slowly comes down the hill, then the P.E gradually decreases, and the K.E gradually increases. This shows the P.E is slowly changing into the K.E. And as it comes down, the K.E increases, and eventually when he stops, then both the K.E and P.E becomes zero.

This changes occurs because energy can never be created nor destroyed, and it changes from one form to another.

The potential energy and kinetic energy are always in flux. At the top of the hill, potential energy is at its highest and kinetic energy is at its lowest because the skateboarder stops for just a moment before being pulled down the hill by the force of gravity. At the bottom of the hill, kinetic energy is the highest because the skateboarder reaches maximum speed.

Explanation:

PLATO

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."

the answer is:

carbon dioxide