Multiple choice

Hydrogen is not found in atmosphere because

  1. it is highly inflammable

  2. it is the lightest gas

  3. it is absorbed by plants

  4. it immediately combines with oxygen to form water
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

While hydrogen is indeed the lightest gas, this is not the complete scientific explanation for its absence in the atmosphere. Being so light, hydrogen atoms can escape Earth's gravitational pull and don't remain concentrated in the lower atmosphere. Additionally, hydrogen is highly reactive and quickly forms compounds (like water with oxygen), so free molecular hydrogen doesn't accumulate. Option B captures the primary reason related to its low density, though the full explanation involves both escape velocity and chemical reactivity.

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