Answer:
The hill models gravity as a driving force in the water cycle.
Explanation:
Gravity (the gravitational force that pulls objects towards the centre of the Earth) drives the water cycle.
Gravity is responsible for precipitation (rain, hail, sleet, and snow) falling downwards towards the Earth's surface. It is also responsible for water at higher points on the Earth's surface flowing downwards to the lower points on the Earth's surface.
In Carlos' model, the hill represents a higher point on the Earth's surface while the valley represents a lower point on the Earth's surface. The river, flowing downwards from Carlos' hill to Carlos' valley, demonstrates the role of gravity as the driving force of the water cycle.
Even though both parents still have blood type A, Dad can pass on either his A or his O gene version. Mom can also either pass on her A or her O. Because of this, you can see that there's 1 in 4 or 25% chance for a child to have OO, or blood type O.
