Correct answer: A. Buddhism
Explanation: The direct answer is A, Buddhism. Sanchi Stupa is a major Buddhist monument complex in Madhya Pradesh. A stupa is a dome-shaped structure traditionally connected with Buddhist relics, remembrance, worship, and the teaching of the Buddha. Sanchi was developed especially during the Mauryan and later periods and is associated with Emperor Ashoka and the spread of Buddhism. Option A is correct because the monument’s religious and historical identity is Buddhist. Option B, Jainism, has its own temples, images, and sacred sites, but Sanchi Stupa is not mainly a Jain monument. Option C, Sikhism, developed much later and is associated with gurdwaras, not this stupa. Option D, Islam, is associated with mosques, tombs, and other Islamic architectural forms; Sanchi is not an Islamic monument. Do not decide only from the word “stupa”; here both the structure and historical evidence point to Buddhism. Memory cue: stupa, Buddha, Ashoka, and Sanchi belong together.