Final answer:
The maximum temperature for thawing ground beef under running water to ensure safety is 70°F (21°C) as per USDA guidelines. Since none of the given options match this, the next safest option is 50°F (10°C), which is below the danger zone for bacterial growth. The option (A) is correct.
Step-by-step explanation:
When a food worker decides to thaw ground beef by submerging it under running water, the maximum temperature that the water can be, as per food safety guidelines set by the USDA, is 70°F (21°C). However, none of the temperature options given directly match this guideline.
The closest temperature that provides a margin of safety to prevent bacterial growth would be 50°F (10°C). It's important to ensure that the water is cold to mitigate the risk of entering the danger zone where bacteria multiply rapidly, which is between 40°F (4°C) and 140°F (60°C). Therefore, option (A) is correct.