A refrigerator uses a gas which can be easily compressed from gas state to liquid state. The compressed gas passes through the condenser where it loses heat to surrounding air (the room or environment say). The liquid (i.e. compressed gas) then goes through the evaporator (which is the wrapped around the icebox - the area you want to cool). Heat is extracted from the icebox (and the frozen food in it say) and it evaporates the liquid back into a gas (remember latent heat of vaporisation is the heat required to turn a liquid into a gas). The gas carries the heat away to the compressor and condenser and it starts all over again. So you want the refrigerant gas to evaporate at as low a temperature as possible - i.e. if you want to make ice cubes there is no point in using a refrigerant that only evaporates between 5 and 10 degrees C! Likewise you need the refrigerant to condense at a low pressure because that will require the least amount of compressor power input. Does that help? :)

I think the answer is wrong:
The refrigerant should have low boiling point and low freezing point.
2) It must have low specific heat and high latent heat. Because high specific heat decreases the refrigerating effect per kg of refrigerant and high latent heat at low temperature increases the refrigerating effect per kg of
refrigerant.
3) The pressures required to be maintained in the evaporator and condenser
should be low enough to reduce the material cost and must be positive to
avoid leakage of air into the system.
4) It must have high critical pressure and temperature to avoid large power
requirements
so the answer is A

so what is the right answer?

high and low (a)

no it is wrong iit is as it is the correct one.Not high and low