Multiple choice

Which of following options is true?

  1. Up to about 15 km above the Earth’s surface, both ozone and chlorofluorocarbons (CFC) are injurious to life.

  2. Up to 15 km above the Earth’s surface, ozone is favorable to life but CFCs are injurious.

  3. Beyond about 20 km above the Earth’s surface, presence of ozone is important to life on Earth and CFCs are favorable.

  4. Beyond about 20 km above the surface of the Earth, ozone is important to life on Earth but CFCs are injurious.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Beyond about 20 km above the surface of the Earth, ozone is important to life on Earth but CFCs are injurious. Ozone gas absorbs the UV-radiation of sun & gets converted into oxygen (O2). This prevents mutagenic activities of UV-radiation of the living world. Each molecule of CFC destroys thousands of molecules of O3. 

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