A、The function of the human immune system. B、The cause of various auto-immune diseases. C、The viruses that may infect the human

My research focus is on what happens to our immune system as we age. So the job of the immune system is to fight infections. It also protects us from viruses and from auto-immune diseases. We know that as we get older, it’s easier for us to get infections. So, older adults have more chances of falling ill. This is evidence that our immune system really doesn’t function so well when we age. In most of our work when we’re looking at older adults who’ve got an illness, we always have to have health controls. So we work very closely with a great group of volunteers called “The 1,000 Elders.” These volunteers are all 65 or over but in good health. They come to the university to provide us with blood samples, to be interviewed and to help us carry out a whole range of research. The real impact of our research is going to be on health in old age. At the moment we’re living much longer, life expectancy is increasing at two years for every decade. That means an extra five hours a day. I want to make sure that older adults are still able to enjoy their old age and that they’re not spending time in hospital with infections, feeling unwell and being generally weak. We want people to be healthy even when they are old.
Questions 19 to 21 are based on the passage you have just heard.
19. What is the focus of the speaker’s research?
20. What are the volunteers asked to do in the research?
21. What does the speaker say will be the impact of his research?