A、Stress factors. B、Working too long. C、TV watching. D、The general American culture. B题目问的是主持人认为是什么造成了睡眠不足，由定位句可知人们在过度工作的时候会睡眠不足

(26) Americans are suffering from a serious sleep deficit while also cutting back on leisure activities as they spend more time at work. A world that "never goes to sleep" offers many diverse activities, but encourages unhealthy and sometimes antisocial lifestyles for America’s adults. Instead of working to live, they are living to work, a shift that has had a profound impact on their personal lives. Adults report spending less time sleeping, whilst engaging in more social and leisure activities. Most Americans say they suffer from sleep problems and when they go to sleep, many sleep alone even if they are married. These are some of the key findings in the National Sleep Foundation’s 2001.
    "Sleep in America" poll, which looks at the relationship between Americans’ lifestyles, sleep habits and sleep problems. Sleep deprivation continues to be widespread in America. According to the NSF poll, (27) 63% of American adults do not get the recommended (28) eight hours of sleep needed for good health, safety, and optimum performance. In fact, nearly one-third report sleeping less than seven hours each week night, though many adults say they try to sleep more on weekends. This poll shows good news and bad news. (29) The good news is that many Americans say they don’t want to give up any more sleep in spite of their hectic lives. And they would sleep more if they were convinced it would contribute to their quality of life.
    The bad news is far too many adults still sacrifice sleep, which is unhealthy and counter-productive. Is getting less sleep a trend in developed society? Perhaps some of you callers may be able to shed some further light. Let’s open up the phone lines at 54 389 282. (30) And we have our first caller now. Please go ahead...
26．What does the host attribute sleep deprivation to?
27．What proportion of Americans do not get enough sleep?
28．How many hours of sleep are recommended for good health?
29．What is the good news about the results of the poll?
30．How will the host spend the remaining part of the show?