A Group of People Comes in with a Supposed Designated

A group of people comes in with a supposed designated driver, but each one of them ends up purchasing multiple drinks. You don't know/remember who the designated driver was supposed to be, but you do know that whoever it was has now had a few drinks. What do you do?

A) Stop alcohol service to all of them immediately.
B) Ask the group who the designated driver is and be sure to stop serving them.
C) Call a taxi for the group and make sure they all get in it.
D) Monitor the amount they've each had to drink and their intoxication levels, and stop serving them accordingly.