Final answer:
Hot foods should be covered in a refrigerator once they have cooled to 80°F (27°C) or below to prevent the growth of bacteria and ensure food safety.
Step-by-step explanation:
The correct answer to the question of at what temperature hot foods placed in a refrigerator should be covered is b) 80°F (27°C) or below. This is to prevent the rapid multiplication of microorganisms that generally occurs at temperatures between 40° and 140°F (4° and 60°C), which can make food unsafe for consumption. It is important to monitor the refrigerator temperature with a thermometer to ensure it stays at or below 40°F (4°C), which inhibits bacterial growth and helps to maintain food safety, especially during a power outage or when cooling hot foods before they are covered and stored.