The answer to this question is : D.
Well if you already have the silver stuff on your tooth the only way to get it out is if your tooth falls out or if the stuff scrapes off...or you could just lower the amount of sugar intake you have.
Hope I could help!!
Answer:
Carbon dioxide
Explanation:
Because The heart pumps the oxygen to the muscles that are doing the exercise. When you exercise and your muscles work harder, your body uses more oxygen and produces more carbon dioxide.