How did South Asia spread its religions and culture to China and south east Asia ?

The arrival of Buddhism in China was officially noted by the imperial court in the mid-1st century CE, and the faith spread in China thereafter, helped by both official and private support for the building of temples and monasteries.About the beginning of the Common Era, Indian merchants may have settled there, bringing Brahmans and Buddhist monks with them. ... Hindu and Buddhist traders, priests, and, occasionally, princes traveled to Southeast Asia from India in the first few centuries of the Common Era and eventually settled there.

i think it is the third one.