In what century was Gru Nanak born?

Nanak, (born April 15, 1469, Rai Bhoi di Talvandi [now Nankana Sahib, Pakistan], near Lahore, India—died 1539, Kartarpur, Punjab), Indian spiritual teacher who was the first Guru of the Sikhs, a monotheistic religious group that combines Hindu and Muslim influences. His teachings, expressed through devotional hymns, many of which still survive, stressed salvation from rebirth through meditation on the divine name. Among modern Sikhs he enjoys a particular affection as their founder and as the supreme master of Punjabi devotional hymnody.

The answer should be a.