What should flight attendants do when the seatbelt sign comes on?

When the seatbelt sign comes on, it is crucial for flight attendants to monitor seatbelt compliance by checking visually. This action is important because it ensures that all passengers are adhering to safety regulations, which is critical during times of turbulence or other in-flight situations that require everyone to be seated with their seatbelts fastened.

Visual monitoring allows flight attendants to assess the cabin and identify those who may not be seated or who have unfastened their seatbelts, enabling them to intervene if necessary to enhance passenger safety. This proactive approach helps prevent potential injuries that could arise from sudden movements of the aircraft.

The other options would not align with the safety protocols expected during these situations. Ignoring the seatbelt sign could lead to dangerous situations in an emergency or turbulent conditions. Making an announcement may be helpful, but ensuring compliance through visual checks is a more direct and effective safety measure. Finally, while notifying the captain about any serious compliance issues could be appropriate, the primary responsibility at that moment is to ensure that passengers are safely buckled in.