The correct answer is: A. Mahabodhi Vihar
Mahabodhi Vihar is a UNESCO World Heritage Site located in Bodh Gaya, Bihar, India. It is a Buddhist temple complex that contains the Mahabodhi Temple, a UNESCO World Heritage Site. The Mahabodhi Temple is a Mahayana Buddhist temple built in the 3rd century BCE. It is the site where Gautama Buddha attained enlightenment under the Bodhi tree. The temple is one of the most important Buddhist pilgrimage sites in the world.
The other options are incorrect because they are not UNESCO World Heritage Sites.
- Buddhist Monastery in Nalanda: Nalanda was an ancient university in India. It was one of the most important centers of learning in the world for over 700 years. The university was destroyed in the 12th century.
- Ancient site of Vikramashila Monastery: Vikramashila was an ancient Buddhist monastery in India. It was one of the most important centers of learning in the world for over 500 years. The monastery was destroyed in the 12th century.
- Tomb of Sher Shah Suri: Sher Shah Suri was a 16th-century Indian ruler. He was the founder of the Sur Empire. His tomb is located in Sasaram, Bihar, India.
I hope this helps! Let me know if you have any other questions.