No spitting public service advertisements

Your asking this question shows that you are a civilized person, because you realize that spitting is not good. In fact, you already have the answer in your heart, but I'd better talk about it. Sputum, runny nose, excrement, etc ... things secreted directly by the human body carry many bacteria and viruses harmful to the human body. When you spit, others will have a sense of crisis. Although it is not direct, they still think that you violated him, so it is unsanitary and very impolite.