There should be options for this question. I managed to find them elsewhere they are:
Reference groups
Social Scripts
frames
norms
The correct answer would be that Bob was surprised because the social scripts did not meet his expectation for that situation. A social script is a series of behaviors, actions, and consequences that are expected in a particular situation or environment. So in this instance when you go to the beach you expect people to be wearing beach/swim wear and not formal attire so Bob was surprised by this unusual behavior.