参考答案：Medical researchers need to understand health problems before they can develop ways to treat them. Some diseases and health problems involve processes that can only be studied in a living organism. Animals are necessary to medical research when it is impractical or unethical to use humans.
Animals make good research subjects for a variety of reasons. Animals are biologically similar to humans. They are susceptible to many of the same health problems, and they have short life-cycles so they can easily be studied throughout their whole life-p or across several generations. In addition, scientists can easily control the environment around the animal (diet, temperature, lighting, etc.), which would be difficult to do with people. However, the most important reason why animals are used is that it would be wrong to deliberately expose human beings to health risks in order to observe the course of a disease.
A few experiments do involve painful procedures because pain is being studied or drugs would interfere with the research. In such cases, scientists are morally and legally obligated to ensure that the procedures are necessary.
Those who work with research animals — scientists, veterinarians, and animal care technicians should care about the animals. They should recognize that using animals in research is a privilege that carries with it the responsibility to treat those animals humanely. Furthermore, pain and distress can literally change how the body functions, so it is also in the best interest of science to provide good animal care.