Hint: Ashoka was one of the most successful and at the time one of the powerful kings of the Mauryan Empire. In the 19th century A.D, when we look at history, a large number of Ashokan edicts came into light from India, Nepal, Pakistan, and Afghanistan. These edicts are mainly adorned on the rocks and the pillars. These edicts declare about the reforms in Ashoka's policies.
Viharas is derived from a Sanskrit word which means dwelling or house. It was the ancient Indian term for a Buddhist monastery. Originally, viharas were the places used by wandering monks during the rainy season for dwelling but eventually, they became changed into centres of learning and Buddhist architecture. Viharas were considered monasteries. The early history of viharas is unclear and there is no evidence for that. In the period of the Maurya Empire the rock-cut architecture was found in cave viharas. When we look at history there are a lot of viharas situated. Some of the viharas become extremely important institutions and others become evolving into Buddhist Universities.
One of the important viharas is to become a University that is Nalanda. There were a lot of viharas to become a change in universities. It was world-famous, and that led to the transmission of Buddhist teachings into other parts of Asia including China and Tibet, where Buddhism continued to increase after its decline in India.
The viharas are also known as the old or early type of Buddhist monastery. The structure of viharas included an open court, cell accessible, and an entrance porch. In India, the viharas are mainly constructed to provide shelter for monks during the rainy season. They used these viharas as a residence for monks, used as a centre for religious work, a centre for meditation, and a centre for Buddhist learning.
Hence, the correct answer is option (C).
Note: King Ashoka mostly used stone architecture with less usage of wood. The whole of his contributions to ancient architecture is unique and that made his works different from others. The main category of Ashoka monuments can be seen in the form of stupas, pillars, and caves.