Trees remove carbon dioxide from the atmosphere. Carbon dioxide is a greenhouse gas that causes global warming.
Trees take in carbon dioxide and release oxygen. Deforestation gets rid of trees, so carbon dioxide is no longer being absorbed. Since carbon dioxide is a greenhouse gas, meaning that it traps heat in the Earth's atmosphere, too much of it causes global temperatures to rise.
Exercise is the primary advice the coaches give to the athletes if they get a cold or any other infection. The main reason behind this advice is the fact that exercising strengthens the immunity of a person. When a person has an infection, the strengthening of the immune system will help his body to efficiently fight against the infectious pathogens. The blood circulation is increased which is involved in the enhancement of the acute immunity of the person.