Which of the following statement is wrong?

• The performance of the vapour compression refrigerator varies considerably with both vaporising and condensing temperatures.
• In vapour compression cycle, the useful part of the heat transfer is at the condenser.
• In ammonia-hydrogen (electolux) refrigerator, no compressor, pump or fan is required.
• The effect of under-cooling the liquid refrigerant is to decrease the coefficient of performance.