Which of the following is not a category into which Ashoka's monuments may be grouped?

Answer: Option C

Viharas as monasteries. The early history of viharas is unclear. Monasteries in the form of caves are dated to centuries before the start of the common era, for Ajivikas, Buddhists and Jainas. The rock-cut architecture found in cave viharas from the 2nd-century BCE have roots in the Maurya Empire period.