Which scenario would be the most problematic, considering the limited usage of the euro?

A. A German family tries to purchase snacks at a French grocery store.
B. A German family attempts to pay for postcard at a French souvenir shop
C. A Danish family attempts to pay for their meal at an Italian restaurant in Sicily
D. An Italian family attempts to purchase tickets for a tour of a German zoo

C. A Danish family attempts to pay for their meal at an Italian restaurant in Sicily