What is the most appropriate way to monitor the temperature in a laboratory refrigerator?

A. Place a thermometer in the refrigerator
B. Open the refrigerator door and wave a thermometer inside, then check the reading
C. Place an ice cube tray in the refrigerator and see if the water freezes
D. Place a bottle of drinking water in the refrigerator and take a drink to determine coldness
E. Open the refrigerator frequently to check items for coldness

Answer: A