Who was the fourth caliph of Islam and a cousin of Prophet Muhammad (PBUH)?

A. Uthman ibn Affan
B. Ali ibn Abi Talib
C. Muawiyah ibn Abi Sufyan
D. Abu Bakr al-Siddiq

Answer: Ali ibn Abi Talib


Additional Information: Ali ibn Abi Talib was the cousin and son-in-law of the Prophet Muhammad and the fourth caliph of Islam.