The correct answer is: a) Tea plantations.
During the colonial period, Assam was a major producer of tea. The British East India Company established tea plantations in Assam in the early 1800s, and these plantations attracted a large number of immigrants from other parts of India. The immigrants were drawn to Assam by the promise of high wages and good working conditions.
The tea plantations were a major source of employment in Assam, and they played a significant role in the development of the region’s economy. The plantations also had a major impact on the social and cultural life of Assam. The immigrants brought with them their own languages, customs, and religions, which helped to shape the unique culture of Assam.
The tea industry in Assam continued to grow in the post-colonial period, and it remains one of the most important industries in the region. The tea plantations are a major source of employment and income for the people of Assam, and they play a vital role in the economy of the region.
The other options are incorrect because they were not major industries in Assam during the colonial period.
Option b) Oil industry: The oil industry in Assam did not develop until the early 20th century.
Option c) Timber trade: The timber trade was an important industry in Assam in the pre-colonial period, but it declined in importance during the colonial period.
Option d) Jute cultivation: Jute cultivation was an important industry in Bengal, but it was not a major industry in Assam.