The migration of people from present-day Jharkhand to Assam during the colonial period was primarily associated with:

Employment in tea plantations.

The correct answer is Option 1: Employment in tea plantations.

Option 1: Employment in tea plantations — Correct. Colonialism led to the movement of people from present-day Jharkhand to Assam to work on tea plantations

NCERT: Colonialism also led to considerable movement of people. It led to movement of people from one part to another within India. For instance people from present day Jharkhand moved to Assam to work on the tea plantations. A newly emerging middle class particularly from the British Presidency regions of Bengal and Madras moved as government employees and professionals like doctors and lawyers moved to different parts of the country. People were carted in ships from India to work on other colonised lands in distant Asia, Africa and Americas. Many died on their way. Most could never return. Today many of their descendents are known as people of Indian origin.