To investigate the relationship between sleep and memory, the researchers conducted the following research. They performed sleep and memory tests on 21-year-olds and 75-year-olds. They performed word memory tests on subjects before falling asleep at night. It shows that the word memory performance of the elderly is about 25% worse than that of young people. During sleep, the researchers used the electroencephalograph to test the subject's sleep and brain wave activity. The elderly had slower-wave sleep than younger ones. The average person is 75% less. On the day after 8 hours of sleep, the researchers again tested the memory of the words before the day. The results showed that the word memory performance of the elderly the next day was 55% worse than that of young people. Therefore, the researchers believe that the slower Reduced wave sleep time is the key to affecting older people's memory. Which of the following, if true, can challenge the above view? ['The change of sleep quality depends not only on the length of Mambo sleep, but also on the length of fast wave sleep.', 'Slow-wave sleep can help transfer newly acquired information from the hippocampal region of short-term memory to the prefrontal cortex of long-term memory.', 'Most elderly people have impaired brain function and memory, and it is difficult to improve memory even if they prolong slow wave sleep.', 'In the experiment, some elderly people in the slow-wave sleep period remembered more words than teachers with longer-wave sleep time.']