Forces other than damaging winds are also at work inside tornadoes. Sometimes, as the twisting funnel passes over a house, the walls and ceiling _1__apart as if a bomb had gone off inside. This _2__is caused by the low air pressure at the centre 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 _3__, about 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 __4__by 10 feet. On each square inch of the building, there is 2 pounds of pressure from the inside that is not balance by air pressure outside the building. On the ceiling, that added up to an _5__ pressure of 57000 pounds. The pressure on the four walls adds up to 172800 pounds.
If windows are open in the building, some of the inside air rushes out through them. This will balance the pressure inside and outside the building. But if the windows are shut _6__,the enormous inside pressure may cause the building to burst.
__7__, heavy rain and hail often occur in thunderstorms that later produce tornados, so people frequently shut all windows to protect their _8__. This may cause far _9__ damage later. For the same reason, tornado cellars must have an air __10__, otherwise , the cellar door might be blown out when a tornado passes over it.
A) Worse
B) Tightly
C) Breakthrough
D) Unfortunately
E) Burst
F) Unfriendly
G) Normal
H) Substance
I) Property
J) Explosion
K) Initial
L) Measures
M) Involves
N) Vent
O) Unbalanced
1、E。前面的主语是复数，后面的apart决定了本题填入一个谓语动词，主语为复数决定填入一个非单三形式的动词
2、J。前面的this,后面的is决定本题填入一个名词单数
3、G.根据前面的air pressure is确定本题填入一个形容词作表语，normal修饰pressure压力最合适
4、L.本题需要填入一个定语从句中的谓语动词，根据空格后的“20 by 10 feet",填入measures
5、O.本题需要填入一个形容词修饰pressure,注意空格前是an,所以只能填入一个元音开头词，答案是unbalanced.
6、B.前面是shut为动词，本空要填入副词来修饰，放眼望去只有两个Ly结尾的单词，轻松排除unfriendly
7、D.学过四级阅读的学生可以回忆起unfortunately是一个转折词放句首
8、I.前面的their决定了本空填入一个名词，备选答案property、substance、measures.由于都不认识，只能3选1
9、A.后面的damage(破坏）决定了本题所要填入的形容词是个消极词，答案为worse.
10、N.根据前面的an确定本题需要填入一个名词单数。
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