Bodo language is primarily spoken in the state of Assam in India. It is one of the official languages of Assam, along with Assamese. Bodo is also spoken in some parts of neighboring states like West Bengal, Meghalaya, and Nagaland.

Here is a detailed explanation of why option 'A' (Assam) is the correct answer:

1. Bodo Language:
Bodo is an indigenous language belonging to the Tibeto-Burman language family. It is predominantly spoken by the Bodo people, who are the largest indigenous community in Assam. Bodo language has its own script called "Deodhai" and is recognized as one of the 22 scheduled languages of India.

2. Assam:
Assam is a northeastern state in India, bordered by seven other states and countries like Bhutan and Bangladesh. It is known for its diverse cultural and linguistic heritage. Assam is home to several ethnic communities, including the Bodo community, who speak the Bodo language.

3. Bodo Territorial Region (BTR):
To protect the rights and interests of the Bodo people, the Bodo Territorial Council (BTC) was formed in 2003. The BTC governs the Bodo Territorial Region, which includes four districts of Assam - Kokrajhar, Chirang, Baksa, and Udalguri. The official language of the BTC is Bodo, which further emphasizes the significance of the Bodo language in Assam.

4. Assam's Language Diversity:
Assam is known for its linguistic diversity, with several languages being spoken by different communities. Assamese is the principal language of the state and is widely spoken by the majority population. However, alongside Assamese, there are several other indigenous languages spoken in Assam, including Bodo, Bengali, Karbi, Mishing, Dimasa, and others.

Overall, Bodo language is predominantly spoken in the state of Assam, particularly in the Bodo Territorial Region. It holds significant cultural and linguistic importance for the Bodo community and is recognized as one of the official languages of Assam.