Genetically modified plants have been useful in:

The correct answer is Option (3) → Making crops tolerant to stresses.

Genetically modified (GM) plants have had their genes changed by manipulation. The changes are made to help farmers, so every real benefit of GM is an improvement. Three of the options state the opposite of a benefit.

Option (1) Increasing post harvest losses — Incorrect. GM has helped to reduce post harvest losses, not increase them.

Option (2) Decreasing crop yield — Incorrect. Pest-resistant and stress-tolerant crops protect and raise the yield.

Option (3) Making crops tolerant to stresses. — Correct. GM has made crops more tolerant to abiotic stresses such as cold, drought, salt and heat.

Option (4) Decreasing efficiency of mineral usage by plants — Incorrect. GM has increased the efficiency of mineral usage, which keeps the soil from losing its fertility early.

NCERT Extract:
Biotechnological Applications in Agriculture – “… Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMO). GM plants have been useful in many ways. Genetic modification has: (i) made crops more tolerant to abiotic stresses (cold, drought, salt, heat). (ii) reduced reliance on chemical pesticides (pest-resistant crops). (iii) helped to reduce post harvest losses. (iv) increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil). (v) enhanced nutritional value of food, e.g., golden rice, i.e., Vitamin ‘A’ enriched rice.”