The correct option, "3 only," is justified as both Ajanta and Mahabalipuram are renowned for their rock-cut monuments, showcasing the artistry of ancient Indian architecture and sculpture. However, they differ significantly in their historical periods and religious affiliations: Ajanta is primarily associated with Buddhism, dating back to the 2nd century BCE to the 6th century CE, while Mahabalipuram, which features Hindu temples and sculptures, was constructed later during the 7th to 9th century CE under the Pallava dynasty. This distinction highlights the diversity and evolution of religious and cultural practices in India, reflecting different socio-historical contexts.