During the reign of Akbar, the northwestern border of the Mughal Empire was the Hindukush mountains. The Hindukush mountains form a natural geographical boundary between the Indian subcontinent and Central Asia. It is located in present-day Afghanistan, extending from the eastern edge of the Iranian Plateau to the Indus River in Pakistan. The Mughal Empire, under Akbar`s rule, expanded its territory to include parts of present-day Afghanistan. The Hindukush mountains served as a strategic frontier, providing a natural defense barrier against invasions from the northwest. It also allowed the Mughal Empire to control trade routes and maintain influence over the region. The correct answer in this case is option 2.