The correct option is D He was living in Sultanpur Lodhi when he atttained enlightenment.
Guru Nanak Ji was living in Sultanpur Lodhi and he went to bathe in the river Bein that ran alongside the town. The guru meditated for three days on the banks of the river and attained enlightenment. Some assumed that he was dead. However, Guru Nanak Ji returned. He was unusually silent for some time after this event. His first words when he did eventually speak were ‘Na Ko Hindu, Na Ko Musalman’ which translates to ‘There is no Hindu, there is no Muslim’.