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 aircraft B．The helicopter C．The hot-air balloon D．The mobile crane 小题2:In the second paragraph, the author tells_________________. A．who suits bungee jumping B．the principle of bungee jumping C．the material used for bungee jumping D．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 jumper B．the height of the jumping place C．the length of the cord D．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 jumping B．remind people of the danger of bungee jumping C．advise people not to take the risk of bungee jumping D．introduce some knowledge about bungee jumping