Every human being, no matter what he is doing, gives off body heat. The usual prob-lem is
Some parts of most modern buildings-theaters and offices as well as classrooms-aremore than amply heated by people and lights and sometimes must be air-conditioned even in winter. 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 re-use it in others.
Along the way, Pitt has learned a great deal about some of its heat producers. The harder a student studies, the more heat his body gives off. Male students emit more heat than female students do, and the larger a student is, the more heat he produces. It is tempting to conclude that the hottest prospect for the Johnstown campus would be a hard-working, overweight male genius.
Until recently, body heat has caused problems because it ______.
A.was difficult to collect
B.came in a variety of forms
C.was difficult to get rid of
D.tended to be absorbed by physical objects