The correct answer is: Dholak, harmonium, and sarangi.
Dholak is a double-headed drum played with the hands. It is one of the most popular folk instruments in India and is used in a variety of genres, including Bhojpuri, Maithili, and Magahi music.
Harmonium is a keyboard instrument that is played by blowing into a mouthpiece. It is a popular instrument in Indian classical music and is also used in folk music.
Sarangi is a bowed string instrument that is played with a bow. It is a popular instrument in Indian classical music and is also used in folk music.
Guitar, drums, and keyboard are not traditionally used in Bihar’s folk music.
Violin, cello, and flute are not traditionally used in Bihar’s folk music.
Sitar, tabla, and bansuri are traditionally used in Indian classical music, but they are not as common in Bihar’s folk music.