In which situation should a passenger be advised to contact a supervisor?

A passenger should be advised to contact a supervisor in the situation where there is a spill of a chemical or fuel. This scenario raises significant safety concerns that go beyond routine customer service issues. Chemical and fuel spills can pose serious health risks not only to the individuals directly affected but also to other passengers and crew on board. It's crucial that this matter is handled by trained personnel who have the skills and authority to manage hazardous situations appropriately.

In contrast, other options, such as a passenger inquiring about refreshments or a bag's weight, are generally within the purview of standard customer service practices. These situations can typically be resolved by flight attendants or ground staff without the need for supervisory intervention. Similarly, advising a passenger when boarding has started is about managing the boarding process rather than addressing immediate safety issues. When safety is a concern, especially involving hazardous materials, the involvement of a supervisor is essential to ensure proper procedures are followed.