Fact 1: Arefrigerator is used for keeping food fresh for a long period of time.

Fact 2: To prevent bacterial food poisoning, the basic rule is to keep hot foods hot and cold foods cold.

Given the two facts above, answer the question "What prevents cold food from growing poisonous bacteria?" with the following options: 
- Dehydration
 - Cooking
 - a hydraulic system
 - sweating
 - refrigerators
 - fur and fat
 - an electric stove
 - hard outer covering


 

     refrigerators    