The correct answer is option 1, 712 A.D.

In 712 A.D., Mohammed-bin-Qasim successfully conquered the region of Sind. He was an Arab general who led an expedition on behalf of the Umayyad Caliphate. His conquest of Sind marked the first major Muslim incursion into the Indian subcontinent. Qasim`s military campaign was prompted by political and economic reasons, as the Caliphate sought to expand its influence and control over lucrative trade routes. Qasim`s conquest of Sind laid the foundation for future Muslim rule in the region, establishing a precedent for further incursions by Muslim rulers into India. This event is significant in the history of the subcontinent, as it marks the beginning of a process that would eventually lead to the establishment of Muslim empires in India.