Which of the following pair is not correctly matched?

The ozone layer lies in the stratosphere, roughly 15 to 35 km above the surface, not in the troposphere. The troposphere is the lowest layer, where weather occurs, and ozone there is a ground-level pollutant. So D is the mismatch.

• Renneting, cheese: rennet (chymosin, traditionally from calf stomach) coagulates milk proteins, the first step in cheese making. Correct.
• Genetic engineering, plasmids: plasmids are circular extrachromosomal DNA in bacteria, used as cloning vectors to carry foreign genes. Correct.
• Golden rice, Vitamin A: engineered to produce beta-carotene, a precursor of Vitamin A, in the endosperm. Correct, though its cultivation approval in India is still not granted.

The core concept is atmospheric structure and ozone depletion, which links to the Montreal Protocol and to GS-III environment questions on ozone-depleting substances in the stratosphere.

Trap: aspirants confuse the location of ozone, picturing ozone pollution near the ground and assuming the layer is in the troposphere.