The primary task of review is to consolidate and deepen the understanding and memory of what you have learned. First of all, we should determine a central content according to the knowledge system of the textbook, focusing on the center, key points and difficulties of the textbook. We will never relax until we really understand it. Secondly, we should consolidate in time to prevent forgetting. It is best to review before forgetting, if you forget, the efficiency will be low. Review regularly and don't catch cold at once.