What is required in a refrigerator at all times, regardless of performance issues?

A thermometer is essential in a refrigerator at all times because it allows for continuous monitoring of the internal temperature, ensuring that food is stored within the safe temperature range to prevent the growth of harmful bacteria. The safe temperature for storing perishable food is generally at or below 40°F (4°C).

If the refrigerator experiences performance issues, such as malfunctioning parts or power failure, having a thermometer in place is crucial to verify that the temperature remains within that safe range. This information can guide timely actions, such as discarding food that may have been exposed to unsafe temperatures for too long.

Regularly checking the thermometer can help maintain food safety standards and prevent foodborne illnesses, which is why its presence is paramount at all times, regardless of the refrigerator's operational performance.

The other options, while potentially useful in certain circumstances, do not provide the same level of essential, continuous monitoring as a thermometer does.