Q: What is the missing first step of the following process:  -  Once in the lungs, oxygen is moved into the bloodstream and carried through your body - At each cell in your body, oxygen is exchanged for a waste gas called carbon dioxide - Your bloodstream then carries this waste gas back to the lungs where it is removed from the blood stream and then exhaled - Your lungs and respiratory system automatically perform this vital process, called gas exchange -
A: He air we breathe contains oxygen and other gases

Q: What is the missing first step of the following process:  -  The wind and water pick up sediment that came off the rocks - Sediment is carried to an area by the wind, water, air, or ice - Sediment is deposited on the same spot many times - The sediment piles on top of other sediment for a long time - The sediment near the bottom is compressed by the weight of newer sediment - The sediment becomes sedimentary rock as it is pushed together by the heavy weight -
A: Wind and water erode rocks

Q: What is the missing first step of the following process:  -  The roots of the growing plants start to break up the rock - The plant acids dissolve the rock - The rock is broken down into smaller pieces - Erosion begins.
A: Plants start growing on or near the rocks

Q: What is the missing first step of the following process:  -  The particles remove small pieces of the rock each time they touch the rocks - The particles continue to hit, brush against, or grow against the rocks - The rock eventually is broken apart by this contact - The pieces of the rock are now small rocks - The rock pieces are worn away into smaller and smaller pieces by the same forces -
A: