单选题
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 envisioned 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 ignition of tons of aviation fuel carried by the aircraft. Steel lightly covered with concrete is the main structural component of the towers and steel loses a lot of structural strength when heated to 1,100 degrees Centigrade and beyond, as it was. To shield the steel the towers beams were coated with a few centimeters of concrete. That insulation was to provide structural integrity 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 knowledgeable 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 remaining part of the building. The mass of the falling top floors created such a falling load that some experts estimate it exceeded by 5 to 10 times normal bearing loads. The effect was like a giant hammer, each floor contributing more weight to be born by the next floor down. Were the Trade Towers well designed? Engineers say yes. But the public believes that architects will never again design a tall building without considering the effects of terrorist attacks of all potential 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.
单选题
This passage is mainly about ______.
【正确答案】
B
【答案解析】解析：本题是主旨题。本文主要探讨的是世贸中心双子楼设计好坏的问题。
单选题
Many engineers after September 11 believe that the Twin Towers were well designed because ______.
【正确答案】
D
【答案解析】解析：本题是细节题。根据文章第一段第2句中的“The buildings were…at the time．”和第3句中的“Indeed，they were…crash into them．”可以推出：许多工程师认为双子楼设计得很好，主要原因是它们在遭受撞机后没有立刻倒塌。
单选题
The word "withstand" in the first paragraph means ______.
【正确答案】
A
【答案解析】解析：本题是词汇题。本题考查对“withstand”的理解。“withstand the force”意思为“to be successful in resisting”(顶住，成功地抵制住)。
单选题
According to the passage, those who designed the towers could have done better if______.
【正确答案】
B
【答案解析】解析：本题推理题。根据文章第一段第4句“They were not…by the aircraft．”，可以推出：设计双子楼的工程师们如果更多地考虑到高温的影响并作出相应的调整的话，结果会好一些。
单选题
Which one is NOT true according to the passage?
【正确答案】
C
【答案解析】解析：本题是推理题。从文章第3段第2句：“Many also agree…the most damage．”可以得出，进行袭击的恐怖者对大楼的设计很熟悉，袭击的要害地点定于易于造成最大损害的90层。选项C“袭击者对双塔不很了解”，与文意不符。但本题是要求找出不正确的选项，所以选C。
单选题
The part of the building below 90th floor______.
【正确答案】
D
【答案解析】解析：本题是推理题。从文中第4段“…the effect was like a giant hammer,each floor contributing more weight to be born by the next floor down．”可以得出，飞机撞至顶层，撞击力像一把锤子，向下面的每层施压下去。由此可以推断：90层以下的楼层是被上层塌下的部分重砸下来的。
单选题
The author believes that the Twin Towers ______.