The correct answer is: a) Dikhu Hydroelectric Project.
The Dikhu Hydroelectric Project is a 200 MW hydroelectric power plant located on the Dikhu River in Nagaland, India. The project was commissioned in 2011 and is owned and operated by the North Eastern Electric Power Corporation Limited (NEEPCO).
The Dikhu Hydroelectric Project is a run-of-the-river project, which means that it does not require a reservoir. The project consists of a 100 m high concrete gravity dam, a 1.5 km long headrace tunnel, a 1.2 km long tailrace tunnel, and a power house with four 50 MW turbines.
The Dikhu Hydroelectric Project is a significant source of electricity for Nagaland and the neighboring states of Assam and Manipur. The project has also had a positive impact on the local economy, providing employment for thousands of people and generating revenue for the state government.
The other options are incorrect because they are not the largest hydropower projects in Nagaland. The Doyang Hydroelectric Project is a 120 MW project, the Dhansiri Hydroelectric Project is a 60 MW project, and the Tizu Hydroelectric Project is a 30 MW project.