The correct answer is: a) Piyali Phukan
Piyali Phukan is an Assamese film directed by Bhupen Hazarika. It was released in 1955 and won the first National Film Award for Best Feature Film. The film is based on the life of Piyali Phukan, a freedom fighter from Assam.
Halodhia Choraye Baodhan Khai is an Assamese film directed by Jahnu Baruah. It was released in 1979 and won the National Film Award for Best Feature Film in Assamese. The film is about a woman who is forced to leave her home and family after her husband is killed in a communal riot.
Era Bator Sur is an Assamese film directed by Bhabendra Nath Saikia. It was released in 1985 and won the National Film Award for Best Feature Film in Assamese. The film is about a man who returns to his village after many years to find that it has been destroyed by a flood.
Dr. Bezbaruah is an Assamese film directed by Atanu Bordoloi. It was released in 2006 and won the National Film Award for Best Feature Film in Assamese. The film is about the life of Dr. Bhupen Hazarika, a renowned Assamese singer, songwriter, and filmmaker.
Piyali Phukan is the correct answer because it was the first Assamese film to win the National Film Award for Best Feature Film. The other films were released after Piyali Phukan.