The largest freshwater lake in Northeast India, Loktak Lake, is located in:

The correct answer is Manipur.

Loktak Lake is the largest freshwater lake in Northeast India. It is located in the state of Manipur, on the Indo-Myanmar border. The lake is a major source of water for irrigation, drinking, and fishing. It is also home to a variety of wildlife, including the endangered sangai deer.

The lake is a Ramsar site, a wetland of international importance. It is also a popular tourist destination.

The other options are incorrect. Assam is the largest state in Northeast India. Nagaland is a mountainous state in Northeast India. Tripura is a state in Northeast India that is known for its tea plantations.