Refrigerators keep food unspoiled because A. at its low temperature, bacteria and moulds are inactive B. at its low temperature, the germs are killed C. at its low temperature, the germs are frozen D. it sterilises the food

The correct answer is: A. at its low temperature, bacteria and moulds are inactive.

Bacteria and molds are the main causes of food spoilage. They grow and multiply at temperatures between 40 and 140 degrees Fahrenheit. By keeping food below 40 degrees Fahrenheit, refrigerators slow down the growth of bacteria and molds, which helps to keep food fresh longer.

Option B is incorrect because bacteria and molds are not killed by cold temperatures. They are only slowed down.

Option C is incorrect because bacteria and molds are not frozen at cold temperatures. They are only slowed down.

Option D is incorrect because refrigerators do not sterilize food. Sterilization is the process of killing all living organisms, including bacteria and molds. Refrigerators do not kill all living organisms, so they do not sterilize food.