Problem: Given the question: What is the missing first step of the following process: - The boiler produces steam under high pressure - The steam generated in the boiler flows down into a cylinder - Just ahead of the wheels, pushing a tight-fitting plunger, the piston - The piston is connected to one or more of the locomotive's wheels through a kind of arm-elbow-shoulder joint called a crank and connecting rod - As the piston pushes, the crank and connecting rod turn the locomotive's wheels and power the train along - An outlet valve opens and the piston pushes the steam back through the cylinder and out up the locomotive's chimney -
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The answer is:
Coal is loaded into the firebox

Problem: Given the question: What is the missing first step of the following process: - Cells with chlorophyll in them capture the light energy - Plants absorb carbon dioxide through their stoma - Plants absorb water through their roots and other parts of themselves - Plants absorb minerals through their roots - Plants convert these inputs into sugars - Sugars can be used as energy sources - Oxygen and water are also produced - Excess water and oxygen are released through stoma and other parts of the plant.
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The answer is:
Sunlight shines on plants

Problem: Given the question: What is the missing first step of the following process: - 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 - They form iron oxide, which is rust -
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The answer is:
Water comes into contact with something made of iron