The rise of Mahajanpadas has NOT been causally linked to:

The threat of foreign conquest

The correct answer is Option (3) → The threat of foreign conquest

Option 1- Growth of trade and Urbanisation.

c.600-500 BCE: Paddy transplantation; urbanisation in the Ganga valley; mahajanapadas; punch-marked coins

From the sixth century BCE, land and river routes criss-crossed the subcontinent and extended in various directions – overland into Central Asia and beyond, and overseas, from ports that dotted the coastline – extending across the Arabian Sea to East and North Africa and West Asia, and through the Bay of Bengal to Southeast Asia and China. Rulers often attempted to control these routes, possibly by offering protection for a price.

Option 2- Extensive use of Iron

The sixth century BCE is often regarded as a major turning point in early Indian history. It is an era associated with early states, cities, the growing use of iron, the development of coinage, etc. It also witnessed the growth of diverse systems of thought, including Buddhism and Jainism.

Option 3- The threat of foreign conquest

The threat of foreign conquest was not a significant factor in the rise of Mahajanapadas. While foreign invasions, such as those of Alexander the Great occurred in the subcontinent, these events came later and are not causally linked to the initial emergence of Mahajanapadas.

Option 4- Agrarian expansion

c.600-500 BCE: Paddy transplantation; urbanisation in the Ganga valley; mahajanapadas; punch-marked coins

Strategies for increasing production: One such strategy was the shift to plough agriculture, which spread in fertile alluvial river valleys such as those of the Ganga and the Kaveri from c. sixth century BCE. The iron-tipped ploughshare was used to turn the alluvial soil in areas which had high rainfall. Moreover, in some parts of the Ganga valley, production of paddy was dramatically increased by the introduction of transplantation, although this meant back-breaking work for the producer. While the iron ploughshare led to a growth in agricultural productivity, its use was restricted to certain parts of the subcontinent.