Efforts are being made to promote and preserve tribal languages of Assam through:

The correct answer is: d) All of the above

Efforts are being made to promote and preserve tribal languages of Assam through documentation and research, language education initiatives, and multilingual policies.

• Documentation and research is important to ensure that tribal languages are recorded and studied so that they can be preserved. This includes collecting oral histories, transcribing and translating texts, and creating dictionaries and grammars.
• Language education initiatives are important to ensure that tribal languages are passed on to future generations. This includes providing language instruction in schools and communities, and creating materials such as textbooks and dictionaries.
• Multilingual policies are important to ensure that tribal languages are given equal status with other languages in Assam. This includes making tribal languages official languages in some areas, and providing funding for language education and other initiatives.

All of these efforts are important to promote and preserve tribal languages of Assam.