Option d is the correct answer. Qandahar was a strategic stronghold for the Mughal Empire. It was located on the trade route between India and Central Asia. It was also a gateway to the Indian subcontinent from the west. The loss of Qandahar to the Safavid Empire in 1638 was a major blow to the Mughal Empire. In 1638, Shah Jahan reclaimed Qandahar from the Iranians; however, despite three campaigns, he lost it once again in 1649. It weakened the Mughal position in Central Asia and made it more difficult to control the trade routes. It also made it easier for the Safavids to launch invasions of the Mughal Empire.