Which of the following is true about class-I and class-II ozone depleting elements? Choose the correct answer from the options given below.

1.Class-I elements have a much higher ozone depleting potential than class-II elements.

2.Class-II elements have a much higher ozone depleting potential than class-I elements.

3.All chlorofluorocarbons belong to class-I ozone depleting elements.

4.HCFC-21 belongs to class-II ozone depleting elements.

5.Class-I contains completely halogenated gases.

A1, 4, 5 only ✓ Correct

B2, 3, 5 only

C1, 3, 4 only

D3, 4, 5 only

Correct answer: (A) 1, 4, 5 only

Explanation

Class-I ozone depleting substances carry a far greater ozone depleting potential than class-II ones.

Statement 1 is right as class-I gases like CFCs and halons are the most destructive to ozone.

Statement 5 is right because class-I gases are fully halogenated, which drives their high potency.

Statement 4 is right since HCFC-21 is a hydrochlorofluorocarbon and belongs to class-II.

Statement 2 reverses the potency and is wrong, while Statement 3 lies outside the counted trio here.

The phase-down began with high-potency class-I gases and then moved to the milder class-II HCFCs.

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