What is the first discourse that the Buddha had delivered at the Deer Park in Sarnath called?

The correct answer is D. Dharmachakrapravartan.

Dharmachakrapravartan is the first sermon that the Buddha delivered at the Deer Park in Sarnath after his enlightenment. It is also known as the “Turning of the Wheel of the Law”. In this sermon, the Buddha taught the Four Noble Truths and the Eightfold Path, which are the foundation of Buddhism.

Mahaparinirvana is the death of the Buddha. Mahamastabhisheka is the coronation of a Jain Tirthankara. Mahabhiniskraman is the Buddha’s departure from his home and family to seek enlightenment.