Hey L (again).
This problem sounds fishy....a furnace moves cool air to a warmer place, and an air conditioner moves warm air to a hotter place. Both of these processes don't happen naturally--the 1st law of thermodynamics states that flow is always from hotter to colder. We can see by the way the problem is stated, something seems out of place.
But, in a furnace/air conditioner that moves air in the opposite direction (cooler to hotter), there must be work done on the system to do this, to reverse the natural process of heat transfer. The electricity supplied to say, your central air system, is what is doing this. This is an example of the 1st law of thermodynamics.
In conclusion, I don't like the way this question is stated....I would say d.