A、Because the hot air has to reach a certain temperature. B、Because the house is very big. C、Because termites try to escape by h

Words come from California of a new weapon in the war on household pests. Two scientists working for a firm in Anaheim, California, have developed a method to eliminate insects without using dangerous chemicals. The new poison? Hot air.
    The basic idea is that insects cannot adjust to temperatures much above normal. In laboratory experiments, cockroaches and termites can’t survive much more than a quarter of an hour at 125 degrees Fahrenheit, or about 50 degrees centigrade.
    The new method involves covering a house with a huge tent and filling it with hot air heated to around 65 degrees centigrade. Hot air is forced in with fans and the tent keeps the heat inside the house. Since termites try to escape by hiding in wooden beams, the heat treatment must be continued for a full six hours. But when it’s all over, and the insects are dead, there are no toxic residues to endanger humans or pets, and no funny smells.
    Scientist claim that there is no danger of fire, either, since very few household materials will burn at 65 degrees centigrade. In fact, wood is prepared for construction use by drying it in ovens at 80 degrees centigrade, which is substantially hotter than the air in this procedure.