The Rendezvous was a significant event and location for the Mountain Men in the early 19th century, primarily during the fur trade era. It was an annual gathering where trappers and traders would meet to exchange goods, specifically pelts, for supplies, as well as socialize and engage in various activities, such as games and competitions.
Out of the options you provided, the best description would be:
"It was where the Mountain Men traded beaver pelts for supplies and where they had fun and games."
This encapsulates the economic and social aspects of the Rendezvous, highlighting its importance as a venue for trade as well as community and cultural exchange among the Mountain Men, trappers, and Native Americans involved in the fur trade.