By the late 1960s, what major achievement did India attain in agriculture?

The correct option is "Became self-sufficient in food grains".

By the late 1960s, India achieved self-sufficiency in food grain production, a milestone primarily driven by the Green Revolution. Initiated in the mid-1960s under the leadership of agricultural scientists like M. S. Swaminathan, the Green Revolution introduced High-Yielding Variety (HYV) seeds, particularly for wheat and rice.
These modern agricultural practices, combined with better irrigation facilities and the structured use of fertilizers and pesticides, drastically boosted India's crop yields. This dramatic increase in domestic production allowed the country to move away from its heavy reliance on food imports, particularly under the US PL-480 program, and establish food security.