Hello!
The answer is: C. 40°F to 140°F
Why?
According to the USDA (United States Department of Agriculture) keeping food at room temperature for too long, will increase the possibility of bacteria creation such as Campylobacter, Salmonella Enteritidis, Escherichia coli, and Staphylococcus aureus.
Temperatures above 40°F thru 140°F creates a most rapid growth environment for bacteria, it's called the danger zone for foods. The recommendations are wether keep the food cold (below 40°F) or keep the food hot (above 140°F).
Have a nice day!