'Manipur' is related to 'Imphal' in the same way as 'Nagaland' is related to '_________'.

Imphal is the capital of Manipur.

Similarly, Kohima is the capital of Nagaland.

Let's explain all the options:

Option (a); Gangtok: Capital of Sikkim.

Option (b); Shillong: Capital of Meghalaya.

Option (c); Aizawl: Capital of Mizoram.

Option (d); Kohima: Capital of Nagaland.

Nagaland: A state in northeastern India

Thus, the correct answer is (D) Kohima.​