Many grocery stores display frozen foods in bins that are open at the top. Why doesn't the warm room air enter the bins and melt the food?

Entry field with correct answer

A. The warm air does enter the bins, but the refrigeration unit keeps the air cold enough to keep the food cold.

B. Fans keep the warm air away.

C. The warm air is blocked from the food by the cold air above the food.

D. Warm air does enter the bins, but it's not warm enough to melt the food.