Through reading this book, I learned the common sense of life: for example, why to cross the street to take the sidewalk, because when we cross the street, if we meet the green light, we have to pass through here, if we don't take the sidewalk, it is easy to have a traffic accident. Sidewalks look like the markings on a zebra, so we call them zebra crossings. Zebra crossings can be seen at traffic junctions in big cities. Why not play on the balcony of a tall building? Because the balcon...