- Water comes into contact with something made of iron - The water combines with carbon dioxide in the air to form carbonic acid - As the acid is formed, the iron starts to dissolve - Some of the water breaks down into hydrogen and oxygen - The free oxygen and dissolved iron bond together What might be the last step of the process?
Ans: They form iron oxide, which is rust

- A large rocky area is formed - The rocky area has a higher elevation than the surrounding areas - Water from precipitation falls in the area - The water forms a stream - The stream flows towards lower elevation - The stream becomes a river - The river continues to flow along the same path for a long time - The river erodes the rocky area that it touches What might be the last step of the process?
Ans: The eroded area cuts deeply into the rock.

- A virus enters a host body - The virus has receptors that lock onto a target cell - The virus enters the cell - The virus uses the cell like a factory to make new copies of the virus - The new copies of the virus leave the cell - Infect other cells What might be the last step of the process?
Ans: The host gets sick as its cells are damaged.

- Sediment settles in a place due to gravity - The sediment breaks down into small particles - Wind or water picks up the sediment - The sediment travels along the same route as the wind or water - The sediment is deposited at new locations by the wind or water - The sediment is picked up again by new wind or water - The sediment travels further What might be the last step of the process?
Ans: The sediment is deposited again in a new place.