11．
Few of us have heard of Nils Bohlin，but whenever we take a car journey his invention makes us safer．Found in almost every modem car，the three-point seat belt reduces our chances of death or injury （伤害）by at least 50%．While feeling thankful to this engineer from Volvo，you may also wonder how he came up with such a great idea．
Having worked as a plane designer before，Nils knew clearly that the pilots were willing to put on anything to keep them safe in an accident，but to his surprise，most people in the cars just didn't want to be uncomfortable for even a minute．To improve the safety for people in the cars，he decided to find a perfect system which should be simple，effective and convenient．In the end，he invented the three-point seat belt，which has been considered as one of the greatest inventions in history．
Seat belts prevent people in the cars from serious injury in five ways．
Keep people inside．People who are thrown out from a car are four times more likely to be killed than those who stay inside．
Protect the strongest parts of the body．Seat belts are designed to fix your body at its strongest parts．For an older child and adult，these parts are the hips （臀部）and shoulders．
Spread out the force in an accident．Seat belts spread the force of the accident over a wide area of the body．By putting less stress on one area，they can help you avoid serious injury．Seat belts also help keep your upper body away from the hard parts of the car if you stop suddenly or are hit by another car．
Help the body to slow down，A quick speed causes injury．With the help of the seat belts，your body can have more time to slow down in an accident．
Protect your brain and spinal cord （脊柱）．Seat belts are designed to protect these two key areas of the human body．Head and spinal cord injuries may be hard to see immediately，but they can cause death．Therefore，it's of great importance to protect these parts．
It takes only a few seconds to buckle up （系好安全带）once you get in the car，but this simple action could save your life．Why wouldn't you？
49．Three-point seat belts reduce chances of death or injury by at least_D．
A.10%
B.30%
C.40%
D.50%
50．Nils Bohlin invented the three-point seat belt in order toD．
A．take a car journey quickly
B．show thanks to the engineer
C．keep the pilots safe in an accident
D．improve the safety for people in the cars
51．From the passage we can learnC．
A．hips and shoulders aren't the older children and adults'strongest parts
B．seat belts can keep your knees and feet away from the hard parts of the car
C．the body has more time to slow down in an accident with the help of seat belts
D．head and spinal cord injuries might be easy to see immediately and cause death
52．This passage is mainly aboutC．
A．how seat belts are made
B．how seat belts are used
C．how seat belts save lives
D．how seat belts develop better．
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