A、A way of bringing back and reusing heat. B、A special form of air conditioning. C、An extra hot water system. D、A method of keep

Every human being, no matter what he is doing, gives offbody heat. The usual problem is how to get rid of it. But the designers of the Johnstown campus of the University of Pittsburgh set themselves the opposite problem — how to collect body heat. They have designed a collection system which[22]utilises not only body heat, but the heat given off by such objects as light bulbs and ice-boxes as well.[23]The system works so well that no general fuel is needed to make the campus’ six buildings comfortable.     Some parts of most modern buildings — theatres and offices as well as classrooms — are more than enough heated by people and lights and sometimes must be air-conditioned even in winter.[24]The technique of saving heat and redistributing it is called "heat recovery". A few modern buildings recover heat, but the University’s system is the first to recover heat from some buildings and reuse it in others.
    Along the way, Pitt has learned a great deal about some of its heat producers.[25]The harder a student studies, the more heat his body gives off. Male students emit more heat than female students, and the larger a student, the more heat he produces. It is concluded that the hottest prospect for the Johnstown campus would be a hard-working, overweight male genius.
22. What do we know about the heat collection system?
23. How many buildings are heated entirely by the heat collection system on Johnstown campus?
24. What does heat recovery refer to, according to the passage?
25. Which of the following kinds of people would produce the least amount of heat?