Correct option is A
The correct answer is (a) Abhinaya Darpana.
The "Abhinaya Darpana" is an ancient text by Nandikeshvara, essential for the study of Indian classical dance, including Bharatanatyam. It specifically focuses on the principles of gesture, posture, and expressions, which are core components in Bharatanatyam choreography and performance. This makes it a direct and critical resource for anyone studying or performing Bharatanatyam.