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。前面的主語是復數，后面的apart決定了本題填入一個謂語動詞，主語為復數決定填入一個非單三形式的動詞

　　2、J。前面的this,后面的is決定本題填入一個名詞單數

　　3、G.根據前面的air pressure is確定本題填入一個形容詞作表語，normal修飾pressure壓力最合適

　　4、L.本題需要填入一個定語從句中的謂語動詞，根據空格后的“20 by 10 feet",填入measures

　　5、O.本題需要填入一個形容詞修飾pressure,注意空格前是an,所以只能填入一個元音開頭詞，答案是unbalanced.

　　6、B.前面是shut為動詞，本空要填入副詞來修飾，放眼望去只有兩個Ly結尾的單詞，輕松排除unfriendly

　　7、D.學過四級閱讀的學生可以回憶起unfortunately是一個轉折詞放句首

　　8、I.前面的their決定了本空填入一個名詞，備選答案property、substance、measures.由于都不認識，只能3選1

　　9、A.后面的damage(破壞)決定了本題所要填入的形容詞是個消極詞，答案為worse.

　　10、N.根據前面的an確定本題需要填入一個名詞單數。