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  3. The opinion of many engineers is that the architects that designed the New York World Trade Center Twin Towers did a good job in

The opinion of many engineers is that the architects that designed the New York World Trade Center Twin Towers did a good job in

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问题     The opinion of many engineers is that the architects that designed the New York World Trade Center Twin Towers did a good job in. designing the buildings. The buildings were safe from the hazards (47)______ at the time. Indeed, they were designed to withstand the force of aircraft that might crash into them. They were not however, designed to withstand the effects of the very high temperatures generated by the (48)______ of tons of aviation fuel carried by the aircraft.
    Steel (49)______ covered with concrete is the main structural component of the towers and steel loses a lot of structural strength when heated to 1100 degrees Centigrade and beyond, as it was. To (50)______ the steel the towers’ beams were coated with a few centimeters of concrete. That insulation was to provide structural (51)______ for at least 1 hour of fire. The towers met that test. The south tower lasted 62 minutes. The north; 103 minutes. Tragedy followed when not all could escape prior to the collapse.
    Most experts agree that the Twin Towers were very well designed. Many also agree that the people planning the attacks were very (52)______ and aimed the aircraft at a height that would effect the most damage. The aircraft crash, and the resulting fuel fed fires were aimed at about the 90th floor. That was just high enough to insure that the upper floors would weaken with the heat and crack down, dropping into the (53)______ part of the building.
    The mass of the falling top floors created such a falling load that some experts estimate it (54)______ by 5 to 10 times normal bearing loads. The effect was like a giant hammer, each floor (55)______ more weight to be born by the next floor down.
Were the Trade Towers well designed? Engineers say yes. But the public refers to the belief that architects will never again design a tall building without considering the effects of terrorist attacks of all (56)______ kinds. That not only includes the ability of the structure to withstand attack but the means to allow the buildings’ occupants to escape in time to survive

             Word Bank:
A. exceeded             I. collision
B. ignition             J. contributing
C. strictly             K. lightly
D. practical            L. knowledgeable
E. integrity            M. replace
F. shield               N. potential
G. remaining            O. happened
H. envisioned

选项
答案F
解析 本空应填入动词原形，选项中的动词有F. shield和M. replace。shield作动词时意为“保护，防护”，to shield the steel可以构成双塔梁架被涂上混凝土的目的，因此答案为F。replace意为“代替，取代”，replace the steel与本段开头的Steel…is the main structural component of the towers矛盾，因此排除M。
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