问题补充：
Bungee jumping is an activity about jumping from a tall structure while connected to a large elastic cord(有弹性的绳子). The tall structure is usually a fixed object, such as a building, bridge or crane; but it is also possible to jump from a movable object, such as a hot-air balloon or helicopter, that has the ability to stay over one place on the ground; fixed-wing aircraft are unsuitable because they only stay high when moving quickly forward.
When the person jumps, the cord stretches to absorb (吸收)the energy of the fall, then the jumper flies upwards again as the cord jumps back. The jumper oscillates(摆动)up and down until all the energy is used up.
The word bungee first appeared around 1930 and was the name for a rubber eraser. The first modern bungee jumps were made on 1 April 1979 from the 250-foot Clifton Suspension Bridge in Bristol, by David Kirk, Chris Baker and Alan Weston of the Dangerous Sports Club. The jumpers continued with jumps in the US from the Golden Gate and Royal Gorge bridges, spreading the concept worldwide. By 1982 they were jumping from mobile cranes and hot-air balloons. Later they put on commercial(商业的)shows, which began in 1986.
As with any sport, injuries can still happen, and there have been deaths. A relatively common mistake in the cases that may cause death is to use a cord that is too long. The cord should be fully shorter than the height of the jumping place to allow it room to jumper either starts to slow down or keeps speeding up depending upon the speed of falling.
【小题1】Which of the following is NOT suitable for bungee jumping?A．The fixed-wing aircraftB．The helicopterC．The hot-air balloonD．The mobile crane【小题2】In the second paragraph, the author tells.A．who suits bungee jumpingB．the principle of bungee jumpingC．the material used for bungee jumpingD．the danger of bungee jumping【小题3】According to the last paragraph, the safety of the jumpers depends mainly on.A．the weight of the jumperB．the height of the jumping placeC．the length of the cordD．the speed of the falling【小题4】The purpose of writing this passage is to.A．teach people how to carry out a bungee jumpingB．remind people of the danger of bungee jumpingC．advise people not to take the risk of bungee jumpingD．introduce some knowledge about bungee jumpingA
答案：
(答案→)A
解析：文章介绍了蹦极跳的一些知识。包括适合这项运动的场合，原理如何保证安全等。
【小题1】细节题：文章第一段的句子：The tall structure is usually a fixed object, such as a building, bridge or crane; but it is also possible to jump from a movable object, such as a hot-air balloon or helicopter,可知答案是A
【小题2】段落主旨题：文章第二段介绍了蹦极跳的原理。选B
【小题3】从文章的最后一段的句子：The cord should be fully shorter than the height of the jumping place to allow it room to jumper either starts to slow down or keeps speeding up depending upon the speed of falling.可知蹦极跳安全的关键是有弹性的绳子。选C
【小题4】主旨题：文章介绍了蹦极跳的一些知识。选D
