A father is teaching his son how to ride a bicycle. My son is seven or eight years old, as tall as a bicycle. After studying for more than half an hour, my son still didn't make any progress. Even if the car didn't fall down at the time, it just walked crooked for a few meters, and even the car and the people fell together. Suddenly, the father solemnly shouted to his son: "Learn to learn to ride a bicycle, pay attention to three points, first of all, you must be straight, don't lean on the b...