The correct answer is option 'B', Bakhtiyar Khilji.

Explanation:
Nalanda University was one of the world's oldest universities, situated in Bihar, India. It was a significant center of learning for Buddhist studies and other subjects such as astronomy, mathematics, and medicine. The university was established in the 5th century AD and existed until the 12th century AD.

Bakhtiyar Khilji was a Turkish military commander who was appointed as the governor of Bihar in the early 13th century by Qutb-ud-din Aibak, the founder of the Delhi Sultanate. In 1202 AD, Bakhtiyar Khilji invaded and destroyed Nalanda University.

Reason for the Destruction of Nalanda University:
There is a debate about the motive behind the destruction of Nalanda University. Some historians believe that Bakhtiyar Khilji attacked the university to eliminate the Buddhist influence in the region. Others believe that the attack was motivated by the desire for wealth and treasure.

Impact of the Destruction:
The destruction of Nalanda University marked the end of the ancient Indian education system. Many scholars were killed, and a vast collection of books and manuscripts were burnt. The attack also had a significant impact on Buddhism in India, as it led to a decline in the popularity of Buddhism in the region.

Conclusion:
In conclusion, Bakhtiyar Khilji was responsible for the destruction of Nalanda University in 1202 AD. The attack had a significant impact on the Indian education system and the popularity of Buddhism in the region.