(三)我停顿了一下,环视学生。“即使对于‘人不能穿墙’这种显而易见的事实,也不能看作天经地义的最后结论。螺旋桨飞机发明后,在飞机上装机枪几乎是不可能的,因为飞速旋转的桨叶对子弹形成了不可逾越的壁障,直到发明了同步装置,使每一颗子弹恰好从桨叶空隙里穿过去,才穿破这道壁障。岩石对光线来说也是不可逾越的,但二氧化硅、碳酸钠、碳酸钙混合融化后,变成了透明的玻璃,同样的原子,仅仅只是 (C) I paused for a moment, looking around students. ”Even the plain, straightforward fact that people can not wear a wall can not be taken for granted as the final conclusion.After the invention of the propeller aircraft, it was almost impossible to equip a plane with a machine gun because the rapidly rotating blades formed the bullet Insurmountable barrier until the invention of the synchronization device, so that each bullet just pass through the voids in the blade to penetrate this barrier before. Rocks are also insurmountable for light, but silica, carbonated Sodium, calcium carbonate mixed melts, becomes a transparent glass, the same atoms, just just