The correct answer is Guru Tegh Bahadur Sahib, who was the 9th Sikh Guru. He served from 1664 to 1675 and is known for his martyrdom. The Sikh Guru line in order is: Nanak, Angad Dev, Amar Das, Ram Das, Arjan, Hargobind, Har Rai, Harkrishan, Tegh Bahadur, and Gobind Singh.