The nurse should assure the patient that black tongue is an expected side effect of taking that particular drug. The active ingredient in the drug contain bismuth. The tongue and the alimentary canal of humans contain trace amount of sulphur, when bismuth comes in contact with this sulphur, bismuth-sulphide will be formed. Bismuth-sulphide is an harmless by product, thus, the tongue discoloration observed in the patient is harmless.<span />
The use of cars can cause chemical pollution by the release of carbon in the air.
Another difference would be that DNA contains the 5 carbon sugar deoxyribose while RNA usually contains the 5 carbon sugar of ribose. One differs from the other, as ribose has an additional hydroxyl group bonded to one of the carbon atoms, where as deoxyribose does not.
The answer to your question is homeostasis
