Buddha delivered his first sermon at __________

The correct answer is B. Sarnath.

Sarnath is a town in the Indian state of Uttar Pradesh. It is located 10 km (6.2 mi) east of Varanasi, on the banks of the Ganges River. Sarnath is a major Buddhist pilgrimage site, as it is the place where the Buddha delivered his first sermon, the Dhammacakkappavattana Sutta.

The Dhammacakkappavattana Sutta is considered to be the founding sermon of Buddhism. In this sermon, the Buddha outlined the Four Noble Truths and the Eightfold Path. The Four Noble Truths are:

1. Suffering exists.
2. Suffering is caused by attachment.
3. Suffering can be ended.
4. The way to end suffering is to follow the Eightfold Path.

The Eightfold Path is a set of eight steps that lead to enlightenment. The eight steps are:

1. Right understanding
2. Right thought
3. Right speech
4. Right action
5. Right livelihood
6. Right effort
7. Right mindfulness
8. Right concentration

The Buddha’s first sermon at Sarnath is considered to be one of the most important events in Buddhist history. It is the event that marked the beginning of the Buddhist religion.

The other options are incorrect because they are not places where the Buddha delivered his first sermon. Sanchi is a Buddhist archaeological site located in the Indian state of Madhya Pradesh. Kapilvastu is the birthplace of the Buddha. Vaisali is an ancient city located in the Indian state of Bihar.