Explanation:

- Bihu is indeed a folk dance from the northeastern state of Assam. It is performed during the Bihu festival, which marks the Assamese New Year and the coming of spring.

- Option:1, Bihar is a state in eastern India known for its rich cultural heritage, but Bihu is not associated with it. Folk dances from Bihar include Jat-Jatin and Sohar-Khilouna.

- Option:2, Arunachal Pradesh is another northeastern state, but it has its own set of traditional dances like the Ponung and Bardo Chham.

- Option:4, Karnataka, located in southern India, has its own cultural dances such as Yakshagana and Dollu Kunitha.

Option:3, Assam is the correct answer.