Indo-Gangetic Plain is mainly known for which type of agriculture?

Intensive subsistence agriculture

The correct answer is Option (3) → Intensive subsistence agriculture.

Intensive subsidence agriculture dominated by crops other than paddy: Due to the difference in relief, climate, soil and some of the other geographical factors, it is not practical to grow paddy in many parts of monsoon Asia. Wheat, soyabean, barley and sorghum are grown in northern China, Manchuria, North Korea and North Japan. In India wheat is grown in western parts of the Indo-Gangetic plains and millets are grown in dry parts of western and southern India. Most of the characteristics of this type of agriculture are similar to those dominated by wet paddy except that irrigation is often used.