Bharatanatyam expresses South Indian religious themes and spiritual ideas of _______.

Correct option is B

The correct answer is (b) Shaivism.
Bharatanatyam is a classical dance form that expresses South Indian religious themes and spiritual ideas, primarily of Shaivism. Shaivism is a major tradition within Hinduism that reveres Shiva as the supreme god. Bharatanatyam performances often depict stories and themes from Hindu mythology, particularly those related to Lord Shiva, along with other deities and spiritual concepts.
Therefore, the correct answer is (b) Shaivism.