The correct answer is C. Bakhtiyar Khalji.
Bakhtiyar Khalji was a Turkic general who conquered Bihar in 1205. He was a general in the army of Muhammad bin Sam, the ruler of the Delhi Sultanate. In 1205, Bakhtiyar Khalji was sent to conquer Bihar. He defeated the local ruler, Jayachandra, and captured the capital city of Patna. After conquering Bihar, Bakhtiyar Khalji continued his conquests in eastern India. He conquered Bengal in 1206 and Orissa in 1211. Bakhtiyar Khalji’s conquests opened up eastern India to Muslim rule. He is considered to be the first Muslim conqueror of Bihar.
A. Malik Ibrahim was a general in the army of Muhammad bin Sam. He was not the first Muslim conqueror of Bihar.
B. Iltutmish was the second sultan of the Delhi Sultanate. He was not the first Muslim conqueror of Bihar.
D. Ali Mardan Khalji was a general in the army of Iltutmish. He was not the first Muslim conqueror of Bihar.