Could you explain this further?

A calorie is a unit of thermal energy equal to 4.184 joules or the amount of energy required to raise the temperature of 1 gram of liquid water 1°C at standard pressure. Sometimes a calorie (written with a lowercase "c") is called a small calories or a gram calorie. The symbol for the calorie is cal.

  the correct answer is : binding price ceilings encourage the formation of a black market

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