4. Which of the following is not needed to make a model of the water cycle?

an energy source
water
a closed container
a drain

5. Which of the following explains why water is a limited resource?

Water is present on Earth in a fixed amount that does not change.
Water is degrading slowly with time.
Only water not present in oceans is available for living things to use.
Once it ends up as groundwater, water is no longer available for living things to use.