Debal was the first important town captured by Muhammad Bin Qasim in ___.

Debal was indeed the first significant town captured by Muhammad Bin Qasim during his conquest of Sindh. This event marked the beginning of Muslim rule in the Indian subcontinent in 712 AD, establishing a foothold for the Umayyad Caliphate.

• A. 'Baluchistan' is incorrect. While geographically close, Debal is located in Sindh, and the initial conquest focused on the Sindh region.
• B. 'Sindh' is correct. Debal was a major port city in the Sindh region, and its capture was a pivotal moment in Muhammad Bin Qasim's campaign.
• C. 'Punjab' is incorrect. Punjab was conquered much later by other Muslim invaders, not during Muhammad Bin Qasim's initial campaign in the early 8th century.
• D. 'Khyber' is incorrect. The Khyber Pass is a mountain pass, not a town, and was not the site of Muhammad Bin Qasim's first conquest.