Correct Answer:
B. Hujjatullah al-Baligha
Shah Wali Ullah Dehlawi was an influential 18th-century Islamic scholar, reformer, and philosopher. His most famous and comprehensive work is Hujjatullah al-Baligha, which delves into the philosophy of Islamic law, the wisdom behind its injunctions, and the universal principles of Islam. It is considered a masterpiece of Islamic thought. Fath-ul-Mubeen and Sirat un-Nabi are significant Islamic works, but they are not attributed to Shah Wali Ullah. Sirat un-Nabi, for example, is famously a biography of the Prophet Muhammad by Shibli Nomani. Therefore, Hujjatullah al-Baligha is the correct answer.