-  Air goes through all the little branches in your lungs to fill up the air sacs, or alveoli - Oxygen goes through the walls of the alveoli and into the capillaries - The oxygen goes into the bloodstream - Oxygen is left and carbon dioxide is picked up - You breathe it out through your lungs -   What might be the first step of the process?
Ans: You breathe in

-  After a rain, water seeps into cracks and pores of soil and rock - The water percolates beneath the land surface - Some of the water reaches a zone where all the cracks and pores in the rock are already filled with water - Rainwater absorbs some carbon dioxide as it passes through the atmosphere and even more as it drains through soil and decaying vegetation - The water combines chemically with the carbon dioxide - A weak carbonic acid solution is formed - This acid slowly dissolves calcite, forms solution cavities, and excavates passageways -   What might be the first step of the process?
Ans: Solution caves are formed in limestone and similar rocks by the action of water

-  Over time, more sediment piles on top - The resulting heat and pressure transforms the organic layer into a dark and waxy substance known as kerogen - Left alone, the kerogen molecules eventually crack - The molecules break up into shorter and lighter molecules composed almost solely of carbon and hydrogen atoms - It will turn into either petroleum or natural gas -   What might be the first step of the process?
Ans: Dead organic material accumulates on the bottom of oceans, riverbeds or swamps, mixing with mud and sand

-  The air enters the mouth and nose - The diaphragm contracts - Air fills all the sacks in the lungs - Oxygen passes through the sacks into capillaries - The blood is passed to the blood in the capillaries - The blood carries the oxygen to the heart - The heart pumps the oxygenated blood to the body.  What might be the first step of the process?
