Problem: Given the 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 -
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The answer is:
People breathe and expel carbon dioxide

Problem: Given the question: What is the missing first step of the following process: - Green house gases enter from the earth - Heat is trapped in atmosphere - Different things on earth are hotter - The overall planet is hotter.
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The answer is:
Suns heat enters atmosphere

Problem: Given the question: What is the missing first step of the following process: - The caterpillar eats constantly until it grows bigger - The caterpillar starts to form a cocoon around itself - The caterpillar becomes a pupa - After some time the cocoon hatches - And a butterfly is born.
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The answer is:
A larva is born