[单项选择]

Forces other than damaging winds are also at work inside tornadoes. Sometimes, as the twisting funnel passes over a house, the walls and ceiling burst apart as if a bomb had gone off inside. This explosion is caused by the low air pressure at the center of a tornado.
The pressure at the center of a tornado is usually 13 pounds per square inch. However, inside the house the air pressure is normal, a bout 15 pounds per square inch. The difference of 2 pounds per square inch between the inside and outside pressure may not seem like much. But suppose a tornado funnel passes over a small building that measures 20 by 10 feet. On each square inch of the building, there is 2 pounds of pressure from the inside that is not balanced by air pres sure outside the building. On the ceiling, that adds up to an unbalanced pressure of 57 600 pounds. The pressure on the four walls adds up to 172 800 pounds.
If windows are open in the building, some of the inside air will rus
A. Why Tornadoes Cause So Much Damage
B. Where Tornadoes Arc Formed
C. How Tornadoes Can Be Prevented
D. When Tornadoes Usually Occur