Agricultural development since the 1960s altered the social structure…

The correct answer is Option (2) → Enrichment of medium and large farmers who adopted the new technologies

Option (1) Enrichment of small and marginal farmers who adopted the new technologies — Incorrect. The gains of the new technologies went to medium and large farmers. Small and marginal farmers are the wrong group, so their enrichment is not the change that altered the rural structure.

Option (2) Enrichment of medium and large farmers who adopted the new technologies — Correct. Agricultural development since the 1960s made the medium and large farmers who adopted the new technologies richer. This enrichment was one way the rural social structure changed.

Option (3) Strengthening of hereditary bonds between landowners and agricultural workers — Incorrect. The change ran the other way. Hereditary bonds between landowners and agricultural workers loosened, and a class of 'free' wage labourers grew.

Option (4) Shift from payment in cash to payment in kind for agricultural workers — Incorrect. The shift is stated backwards. As farming became commercialised, workers moved from payment in kind (grain) to payment in cash.