This is not one of the state of 7 sister state.

The term "Seven Sister States" refers to a specific group of seven states located in the northeastern part of India. These states are Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, and Tripura. The term "Seven Sister States" is used to describe the unique geographical and cultural identity of these states, which are distinct from the rest of India.

Each of these states has its own unique history, culture, and geography. They are characterized by their mountainous terrain, dense forests, and diverse ethnic groups. The term "Seven Sister States" was coined to highlight the unity and diversity of these states, which share many commonalities but also have their own distinct identities.

Bihar, on the other hand, is a state located in the eastern part of India. It is not part of the northeastern region and does not share the same geographical and cultural characteristics as the Seven Sister States. Bihar is known for its rich historical and cultural heritage, including ancient sites such as Bodh Gaya, which is a significant pilgrimage site for Buddhists.

The confusion might arise because both the Seven Sister States and Bihar are located in the eastern part of India. However, the Seven Sister States are specifically located in the northeastern region, which is geographically and culturally distinct from the rest of India. Bihar, while also in the east, is not part of this northeastern region.

In summary, the Seven Sister States are a specific group of seven northeastern states in India, and Bihar, being located in the eastern part of India but not in the northeastern region, is not one of these states. Therefore, the correct answer is that Bihar is not one of the Seven Sister States.