Detailed Explanation:

Correct Answer: ✅ Option 3 (I, II and III)

All three statements correctly describe the role of the atmosphere in maintaining Earth's temperature. The atmosphere acts like a thermal blanket by absorbing and trapping heat, preventing the Earth from becoming extremely cold. Greenhouse gases such as carbon dioxide, methane, and water vapour are especially effective in trapping outgoing infrared radiation.

✅ Statement I is Correct: Without the atmosphere, Earth would lose most of its heat to space, and average surface temperatures would be well below freezing.

✅ Statement II is Correct: The atmosphere absorbs and retains heat, maintaining a habitable average temperature through the natural greenhouse effect.

✅ Statement III is Correct: Greenhouse gases such as carbon dioxide, methane, and water vapour efficiently absorb and trap infrared radiation.

Short Notes: Greenhouse Effect

• The natural greenhouse effect keeps Earth warm enough to support life.

• Earth's average temperature is about 15°C with the atmosphere.

• Without the atmosphere, the average temperature would be around –18°C.

• Carbon dioxide (CO₂), methane (CH₄), and water vapour are major greenhouse gases.

• Greenhouse gases absorb outgoing infrared radiation emitted by Earth's surface.

• The greenhouse effect is a natural process, but excessive greenhouse gases enhance global warming.

• Water vapour is the most abundant natural greenhouse gas.