The correct answer is: A. Vaishali
Shanti Stupa is a Buddhist monument located in Vaishali, India. It was built in 1969 by the Japanese Buddhist monk Nichidatsu Fujii. The stupa is a symbol of peace and harmony, and it is a popular tourist destination.
Vaishali is a city in the Indian state of Bihar. It is one of the oldest cities in India, and it is considered to be one of the most important Buddhist sites in the world. Vaishali was the capital of the Vajji confederacy, and it was the site of the first Buddhist council.
The other options are incorrect because they are not districts in which Shanti Stupa is located. Bhagalpur is a city in the Indian state of Bihar. Gopalganj is a city in the Indian state of Bihar. Saran is a district in the Indian state of Bihar.