Many rivers in Assam are considered sacred, with the Brahmaputra being known as:

The correct answer is: a) Luit.

The Brahmaputra is known as the Luit in Assam. It is the longest river in India and the third longest river in Asia. It is also one of the most important rivers in the world, as it provides water for irrigation, drinking, and transportation. The Brahmaputra is also a sacred river for Hindus and Buddhists.

The other options are incorrect because:

• Manas is a river in Assam that is known for its wildlife sanctuary.
• Dhansiri is a river in Assam that is known for its fishing.
• Sonai is a river in Assam that is known for its scenic beauty.