The correct answer is (b) Harsewak Das.
Harsewak Das was the Mahant of Guru Ram Rai Darbar during the Gorkha possession of Dehradun. He was a disciple of Guru Ram Rai and was appointed as the Mahant in 1790. He served as the Mahant for 25 years and died in 1815.
Guru Ram Rai was the fifth Guru of the Sikh faith. He was born in 1635 in Delhi. He was the son of Guru Har Rai and Mata Sujan Kaur. He was appointed as the Guru in 1661 after the death of his father. He served as the Guru for 16 years and died in 1687 in Dehradun.
The Gorkha possession of Dehradun was a period of time when the Gorkha army occupied the city of Dehradun. The Gorkha army was led by Prithvi Narayan Shah. The Gorkha army occupied Dehradun in 1790. The Gorkha army remained in Dehradun until 1815.
Guru Ram Rai Darbar is a Gurdwara located in Dehradun. The Gurdwara was built in 1675 by Guru Ram Rai. The Gurdwara is a place of worship for Sikhs.