The temperature danger zone for time/temperature control for safety food is considered to be

Danger zone is between 4 and 60 degrees C.
Below 4 degrees (refrigerator is between 0 and 4), bacteria grow very slowly.
Above 60 degrees, (most) bacteria will be killed.
Below freezer temperatures (-18), bacteria stop multiplying.
That is why between 4 and 60, it is the danger zone for food safety.

By the way, please put an underscore where you expect an answer.  Otherwise it looks like an incomplete sentence, like " for safety food is considered to be"  Thank you.