Buddhism was india’s dominant religion in 100 bce, and then it

After 100 BCE, Buddhism declined in India: especially during the Gupta time when Hinduism was gaining in importance.

However, it was spreading to other parts of Asia, where it was very popular, 
for example in China, Thailand and Sri Lanka, where significant buddhist communities are found today.

It is c because it shows how the author is stating their own oppinion about the protagonist