You Are Serving a Group of Foreign Tourists

You are serving a group of foreign tourists. Their passports say they are only 18 and 19 years old, but you know that the drinking age where they are from is 18 rather than 21. To comply with the law, what do you do?

A) Serve them since it is legal in their country. After all, that is where their identification is from.
B) Get permission from the manager to serve them.
C) Only serve them beer and wine - no hard liquor.
D) Refuse to serve them any alcohol at all and explain that the domestic drinking age is 21.