The correct answer is: a) Present-day Punjab (India & Pakistan), Kashmir, parts of Afghanistan.
Maharaja Ranjit Singh was the founder and first Maharaja of the Sikh Empire, which ruled over the northwestern Indian subcontinent from 1799 to 1839. The empire at its peak extended from present-day Punjab (India & Pakistan) to Kashmir, parts of Afghanistan, and the Hindu Kush mountains.
Option b) is incorrect because Bengal, Gujarat, and Maharashtra were not part of the Sikh Empire. These regions were ruled by the Mughal Empire at the time.
Option c) is incorrect because Tamil Nadu, Kerala, and Assam were not part of the Sikh Empire. These regions were ruled by the Nayak dynasty, the Ahom kingdom, and the Koch dynasty, respectively.
Option d) is incorrect because Nepal, Bhutan, and Tibet were not part of the Sikh Empire. These regions were ruled by the Shah dynasty, the Drukpa Kagyu school of Tibetan Buddhism, and the Qing dynasty of China, respectively.