Problem: - Several types of gases form in the atmosphere - May come from different sources - The gases remain trapped in the atmosphere - Through the suns light the gases hold in heat and energy - Trap them in our atmosphere What might be the last step of the process?

A: The earth may become warmer this way.

Problem: - Minerals fill spaces between bits of sediment - The sediments become glued together - The glued together parts become hard like cement - The sediment becomes a big rock - The rocks erode slowly - The rocks come apart - The rocks become smaller rocks - The rocks continue to erode into smaller rocks What might be the last step of the process?

A: The process starts again.

Problem: - Ice forms inside a cloud - Ice inside the cloud bumps around and causes electrostatic charges - The cloud becomes a thundercloud - Electrostatic energy builds and forms a strong negative charge - Positive energy is attracted to the negative energy in the cloud - This positive energy gathers on the ground What might be the last step of the process?

A: The positive energy connects with the negative energy and forms lightning.

Problem: - A person breathes in oxygen - The oxygen passes through the bronchial tubes to the lungs - The oxygen is moved into the bloodstream - Circulates through the body - The cells in the body exchange the oxygen with carbon dioxide - The bloodstream carries the carbon dioxide back to the lungs What might be the last step of the process?

A:
The lungs expel the carbon dioxide through the nose and mouth.