Problem: What is the missing first step of the following process: - Makes water acidic - Kills fish - Kills the soils in trees - Leaves are also harmed.

A: Acid rain enters the atmosphere and lands

Problem: What is the missing first step of the following process: - The wind or water deposits tiny rocks - The rocks become known as sediment - The layers of sediment are pressed together by other layers of sediment on top - Minerals from the rocks in the sediment dissolve - Minerals glue the sediment together into a single rock.

A: Wind or water breaks small pieces off of a rock

Problem: What is the missing first step of the following process: - Mix gets inducted into cylinder - Piston compresses the mix - Spark plug emits a spark that ignites it causing combustion - Combustion gases expand - Pushes piston during power stroke - Exhaust valve opens to vent exhaust out tail pipe.

A: Fuel mixes with air

Problem: What is the missing first step of the following process: - A muscle fiber gets a signal from its nerve - Proteins and chemicals release energy to either contract the muscle or relax it - When the muscles contracts the bones connected to he muscle are pulled closer together - When the muscle relaxes the bones move farther apart.

A:
Muscles work by expanding and contracting