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b. rescue teams were formed
c. an alarm system was set up
d. a flood wall was built
12.the purpose of the exercise flood call is to ______.
a. train the civil service for the flood  b. prevent the flood from happening
c. fill people in london with alarm   d. prepare people against floods
13. the author quotes(引述) the woman to _______.
a. describe how frightened most of the londoners were
b. argue that it’s impossible to prevent floods in london
c. show that most londoners took exercise flood call calmly
d. prove that exercise flood call did cause a lot of trouble to londoners
d
before a new type of airplane goes into service, every part of it is tested again and again . but there are two tests that are more important than all the others.
the first is called the “tank test”. a modern airplane must fly very high in the sky. air must be pumped into the plane so that the passengers can breathe. the metal structure of the plane has to be very strong for this reason. when the plane is filled with air, the air presses against the skin of the plane inside. the pressure on a small window is like a huge foot that is trying to get out. if a small part of the plane were to fail, the plane would explode in the sky. to test the structure of the plane, the plane is lowered into a huge tank or container of water. then it is filled with air. the pressure inside the plane is greater than it ever will be when it is high up in the air. finally, there is explosion. this does not cause so much damage inside the water tank as it would anywhere else. engineers can discover which part of the plane has broken. then that part is made stronger.
the most dangerous test happens when the new plane is going through test flights in the air. the test pilot must find out exactly what happens when the engines are all shut off at once. the plane begins to fall like a stone. it is the pilot’s job to find out how he can get control of the plane again. these two tests are examples of how planes are made safe before they ever carry passengers.
14. by doing the “tank test”, the engineers can find out ________.
a. the amount of air in the plane    b. the strength of the plane structure
c. the pressure inside and outside the plane   d. the power of the plane engines
15. what will happen to the plane under the “tank test”?
a. it will be broken.   b. it will be made stronger.
c. it will be filled with water.   d. it will be tested by pilots.
16. according to the text, why are test flights most dangerous?