Concept:Tourism is an ancillary to trade that encourages cultural exchange and social interaction among people across the world.
Explanation:Ancillaries to trade are services that support the buying and selling of goods.
Transportation, communication, tourism, and insurance are all aids to trade.
However, tourism specifically involves people travelling to different places for leisure, sightseeing, and cultural experiences.
Through tourism, visitors learn about local traditions, customs, and ways of life.
This interaction helps to promote socio-cultural development globally.
Transportation and communication mainly assist trade physically or informationally, while insurance provides risk coverage.
Only tourism directly fosters social and cultural exchange between communities.
Answer:C. tourism