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The Amazing Race 20 is the twentieth installment of the reality television show The Amazing Race. The Amazing Race 20 features eleven teams of two, each with a pre-existing relationship, in a race around the world.。子弹经过两百年的科学研究，从一个简单的铅球，变成性能极佳的弹药。科学新发现将介绍子弹的科学，以及子弹如何凭科技的进步，演化为现在的弹药。。