题目

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 s5、如图中表示两种不同元素的原子，下列方框中表示混合物的是（　　）A、B、C、D、