Environmental Science
Biogas is composed of

ethane, carbon dioxide, nitrogen and hydrogen
methane, carbon dioxide, nitrogen and sulphur
carbon dioxide, nitrogen and hydrogen
methane, carbon dioxide, nitrogen and hydrogen

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Environmental Science
The atmosphere near the earth's surface is "heated from below." Which of the following does not significantly contribute to this heating?

Convection from a hot surface
Conduction of heat upward from a hot surface
Heat energy from the earth's interior
Absorption of infrared energy that has been radiated from the surface

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