A、By recording the time people spend on TV. B、By tracking people’s living habits. C、By using memory and fluency tests. D、By scan

Watching more than three hours of television a day doubles memory loss in older people, a new study of more than 3,000 adults suggests. Scientists at University College London used memory and fluency tests on the same group of people six years apart. They found that those who watched on average less than three hours’ television a day showed a decline of around four to five percent, while those who tended to watch more than three hours a day declined by an average of eight to ten percent. The research team say they believe the "alert-but-passive" nature of television watching may be creating stress on the mind, which contributes to memory decline. Older people who watch more television are also less likely to undertake activities known to preserve mental functioning such as reading, or interactive screen-based pursuits such as using the Internet or playing video games. The researchers say that television viewing may be a risk factor for Alzheimer’s disease, but more research is needed to establish a link. While watching television may have educational benefits and relaxation benefits, the researchers advise that adults over the age of 50 should try and ensure that television viewing is balanced with other contrasting activities. If you’re concerned that the amount of television you’re watching could have a negative impact on your health, you should limit the amount of TV you watch each day and undertake some healthy hobbies.
22. By what means did scientists at University College London measure memory loss?
23. What contributed to memory decline in the participants?
24. What do the researchers say about their finding concerning the link between TV viewing and Alzheimer’s disease?
25. What do the researchers suggest older people do?