The correct answer is B. Kesaria.
A stupa is a mound-like structure that was used as a Buddhist monument. It is typically built over the remains of a Buddhist saint or over an object that is sacred to Buddhists. Stupas are often decorated with religious symbols and images.
The Kesaria stupa is located in the Indian state of Bihar. It is one of the largest stupas in India and is believed to have been built in the 3rd century BC. The stupa is made of brick and is decorated with terracotta plaques. It is a UNESCO World Heritage Site.
The other options are incorrect because they do not have stupas that date back to 200-700 AD.
A. Jehanabad is a city in the Indian state of Bihar. It is not known to have any stupas that date back to 200-700 AD.
C. Sitamarhi is a city in the Indian state of Bihar. It is not known to have any stupas that date back to 200-700 AD.
D. Siwan is a city in the Indian state of Bihar. It is not known to have any stupas that date back to 200-700 AD.