The odd one out from the given group is option 'D) Kohima'. Here's an explanation of why:

1. Mizoram:
Mizoram is a state located in the northeastern part of India. It shares its borders with three other northeastern states – Tripura, Assam, and Manipur. The capital of Mizoram is Aizawl. It is known for its beautiful landscapes, rich cultural heritage, and traditional festivals.

2. Sikkim:
Sikkim is also a state in the northeastern region of India. It is bordered by Nepal, Bhutan, and Tibet. The capital of Sikkim is Gangtok. Sikkim is famous for its stunning mountains, including the third highest peak in the world, Kanchenjunga. It is known for its biodiversity, Buddhist monasteries, and adventure tourism.

3. Manipur:
Manipur is another state in northeastern India. It shares its borders with Nagaland, Mizoram, Assam, and Myanmar. The capital of Manipur is Imphal. It is known for its natural beauty, cultural diversity, and Manipuri dance. Manipur is also called the "Land of Jewels" due to its rich tradition of handloom and handicrafts.

4. Kohima:
Kohima is the capital city of Nagaland, which is also a state in northeastern India. Nagaland is known for its vibrant tribal culture and festivals. However, Kohima is not a state but a city within the state of Nagaland. Therefore, it is the odd one out in this group as it does not represent a separate state like Mizoram, Sikkim, and Manipur.

In summary, while Mizoram, Sikkim, and Manipur are all states in northeastern India, Kohima is the capital city of Nagaland, which is the odd one out in this group.