Milindapanho, also known as `The Questions of King Milinda` or `Milinda Panha`, is an ancient Indian text which presents Buddhist philosophy in the form of a dialogue between King Menander (also known as Milinda) and a Buddhist monk.

Option 1: Nagasena is the correct answer. Nagasena is the Buddhist monk who engages in dialogue with King Menander about complex philosophical questions in `Milindapanho`. The text is highly valued for its clear exposition of Buddhist doctrines.

Option 2: Nagarjuna is an incorrect choice. He was an Indian Mahayana Buddhist philosopher and the founder of the Madhyamaka (Middle Path) school of Buddhist philosophy, not associated with `Milindapanho`.

Option 3: Nagabhatta is also an incorrect choice. Nagabhatta was a philosopher, but he was associated with the Hindu Vedantic tradition, not Buddhism, or the `Milindapanho`.

Option 4: Kumarilabhatta is not correct either. He was an Indian philosopher and scholar, one of the leaders of the Mimamsa school of philosophy, not related to `Milindapanho`.