The Battle of Saraighat (1671) was a significant event in Assamese history because it marked:

Ahom victory over Mughals
Expansion of the Koch kingdom
Chutiya kingdom's rise to power
Dimasa Kingdom's defeat

The correct answer is: a) Ahom victory over Mughals.

The Battle of Saraighat was fought in 1671 between the Ahom kingdom of Assam and the Mughal Empire. The Ahoms were victorious, and the battle marked a turning point in the history of Assam. It prevented the Mughals from conquering Assam and ensured the continued independence of the Ahom kingdom.

The Mughals had been trying to conquer Assam for several decades, but they had been unsuccessful. The Ahoms were a powerful kingdom with a strong military. They were also well-organized and had a good understanding of the terrain in Assam. The Mughals, on the other hand, were not familiar with the terrain and were not as well-organized as the Ahoms.

The Battle of Saraighat was fought on the Brahmaputra River. The Ahoms had built a series of fortifications on the riverbank, and they used these fortifications to their advantage. The Mughals tried to cross the river, but they were unable to do so because of the Ahom fortifications. The Ahoms also used their knowledge of the terrain to their advantage. They attacked the Mughals from the rear, and the Mughals were caught off guard.

The Battle of Saraighat was a decisive victory for the Ahoms. It prevented the Mughals from conquering Assam and ensured the continued independence of the Ahom kingdom. The battle is still celebrated in Assam today, and it is considered to be one of the most important events in the history of the state.

The other options are incorrect because they do not accurately describe the Battle of Saraighat. Option b) is incorrect because the Battle of Saraighat did not mark the expansion of the Koch kingdom. Option c) is incorrect because the Battle of Saraighat did not mark the Chutiya kingdom’s rise to power. Option d) is incorrect because the Battle of Saraighat did not mark the Dimasa Kingdom’s defeat.