Answer: Decreases the rate of reaction
Does not decrease the rate of reaction
Explanation: Dehydration of food excludes water from food which is one of the factor needed by microorganisms for growth, so it decreaese the rate of reaction.
Transporting food in refrigerated trucks lowers the temperature of food and not many microorganisms are active at very low temperatures, so it decreases the rate of reaction.
Storing food in airtight containers excludes air which is one of the factors required for microbial activity, so it decreases reaction rate.
Storing food in refrigerators after opening also lowers the temperature of food and hence the the rate of microbial activity.
Storing food in the open air does not decrease microbial activity instead it provides microorganisms with the favorable conditions for their activity such as air and water from water vapor in the air.
Placing food on a warm surface does not decrease rate of reaction because microorganisms are very active in warm and humid environments.