Option c is the correct answer. Bakhtiyar Khalji, a Turko-Afghan military general and a slave under Muhammad Ghori, conquered Bengal and Bihar. He led the Ghurid Empire's military force to conquer eastern India in the late 12th and early 13th centuries. Bakhtiyar Khalji's campaigns resulted in the subjugation of Bihar and the establishment of his rule in Bengal. Bakhtiyar Khalji is known for founding the Khalji dynasty of Bengal, which ruled from 1203 to 1227 CE. His invasions had significant impacts on the region, leading to the displacement of Buddhism and the establishment of Islamic rule in Bengal.