The correct answer is: a) Swift and brutal.
The British suppression of the Revolt in Assam was swift and brutal. The British East India Company had been in control of Assam since 1826, and the local population had been growing increasingly resentful of British rule. In 1857, the Sepoy Mutiny broke out in northern India, and the Assamese joined in the rebellion. The British responded quickly and decisively, and the rebellion was crushed within a few months.
The British suppression of the Revolt in Assam was brutal. Many rebels were killed, and others were imprisoned or exiled. The British also destroyed many villages and crops, and they imposed heavy taxes on the local population. The suppression of the Revolt in Assam had a devastating impact on the region, and it took many years for the people of Assam to recover.
The other options are incorrect. Option b) is incorrect because the suppression of the Revolt in Assam was not long and drawn-out. The rebellion was crushed within a few months. Option c) is incorrect because the British suppression of the Revolt in Assam was not surprisingly lenient. The British responded quickly and decisively, and the rebellion was crushed with brutality. Option d) is incorrect because the suppression of the Revolt in Assam was not mostly unnecessary due to limited unrest. The British suppression of the Revolt in Assam was a brutal and necessary response to a serious rebellion.