Assertion (A): Liquid ammonia is used as a refrigerant in ice plants.

Reason (R): CFC, the main refrigerant, causes global warming.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Both A and R are true but R is not the correct explanation of A.

Explanation — Liquid ammonia is used as a refrigerant in ice plants because anhydrous ammonia is a clear, colourless liquid under pressure. It evaporates rapidly and produces cooling effect. This makes ammonia a good refrigerant. Hence, the assertion (A) is true. CFC, the main refrigerant, decompose by ultraviolet rays to form free chlorine radicals. These free radicals contribute to global warming and ozone depletion. Hence, the reason (R) is true.

Since, reason (R) doesn't explain why liquid ammonia is used as refrigerant in ice plants, it is not the correct explanation of assertion (A).