While studying a strain of infectious bacteria, scientists find that a certain chemical stops the bacteria from multiplying. They develop a drug that contains the chemical. Before releasing the drug for widespread use, which of the following should the scientists do to learn more about how the drug works? A. use a computer model to predict the action of the drug B. observe the drug's effects on the bacteria with a microscope C. study how the drug affects people in an experimental trial D. all of these