Which source of energy do refrigeration systems and heat pumps have in common?
air
ground
water
sunlight

A) Air

Explanation:

In refrigerator system the compressor will compress the gas at high pressure so that its temperature is too small and if is passed through the air inside the refrigerator.

When this low temperature gas is passed through the air inside the refrigerator then it will extract the heat from the space or air at high temperature and hence it is the source of energy inside the refrigerator.

Heat pumps are used in in cold atmosphere where we require thermal energy to keep the temperature high. Here compressor will work on the gas so that it will absorb the heat from surrounding air and release it to the room or inside space.

So here in both cases the source of energy here is Air which will give heat to the system.