Which of the following is not a safe practice for thawing frozen food?

Thawing food safely is crucial in preventing the growth of harmful bacteria that can lead to foodborne illness. Thawing at room temperature is unsafe because it allows the outer layer of the food to reach temperatures that can promote bacterial growth, while the inner parts may still be frozen. This creates an environment where bacteria can multiply rapidly as they thrive in the temperature danger zone, which ranges from 4°C to 60°C (39°F to 140°F).

In contrast, thawing in the refrigerator, under cold running water, or in the microwave involves methods that help keep the food at a safer temperature. Thawing in the refrigerator maintains a consistent and safe temperature, minimizing any risk of bacteria growth. Thawing under cold running water quickly reduces the food's temperature, similarly keeping it out of the danger zone. Using the microwave to thaw food also allows for safe and quick defrosting as long as the food is cooked immediately after. These methods ensure the food remains safe to consume, making room temperature thawing the only unsafe practice among the options presented.