【答案解析】A habit is gradually developed, whether it is good or not. An invisible power drives one doing the same thing repeatly, then it would become a habit. Once a habit is formed, it is difficult to get rid of it. So it is important for us to be careful when we are getting into a habit. Children often tend to form bad habits, some of which are retained until they die. Elder people can also develop bad habits which can ruin people under certain circumstances.