input question: What is the missing first step of the following process: - Engines produce carbon dioxide - Living things produce waste - Waste decomposes - Decomposition produces methane - Water evaporates - Water vapor joins the atmosphere - Carbon dioxide, water vapor and methane are greenhouse gases -???
output answer: People breathe and expel carbon dioxide

What is the missing first step of the following process: - Food is squeezed down the esophagus when you swallow - Acid and enzyme in the stomach break the food down - Releases nutrients - Food then pumped into small intestine - Fluid and enzymes from liver and pancreas pumped into small intestine - Help break food into smallest molecules - Nutrients pass through wall of small intestine - Nutrients absorbed into blood stream - Unused materials passed into large intestine to become fecal matter.
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Answer: An enzyme in saliva begins to break down carbohydrates

Q: What is the missing first step of the following process: - Composition of blood is regulated - Volume of water in blood is kept constant - PH is kept at a constant level - Kidneys help regulate blood pressure - Kidneys stimulate the making of red blood cells - Calcium levels are maintained.
A: Kidneys filter waste out of blood

Question: What is the missing first step of the following process: - They are buried under layers of soil - Pressure builds over time - The remains liquefy - The carbon atoms rearrange to become a new substance.
Answer: Plants and animals long ago died

[Q]: What is the missing first step of the following process: - 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 -
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[A]: You breathe in

Problem: Given the question: What is the missing first step of the following process: - The sediment rolls down hill towards a river - The heavy items sink to the bottom - The lighter items float on the top and in convection cycles - As the river flows the sediment is moved - The sediment gets dumped through tributaries into lakes and the ocean - The sediment keeps moving around the world in convection currents.
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The answer is:
Sediment becomes loose from the rest of the soil