听力原文：A new report says an estimated 50 million to 70 million Americans have sleep problems. It says ninny more are suffering from lack of sleep.
A group of sleep research organizations asked the Institute of Medicine to study the problem. The institute is part of America's National Academy of Sciences. The study examined why we need sleep, the effects of sleep loss and other sleep dimmers. A fourteen-member committee carried out the study. The Institute of Medicine reported their findings earlier this month. The report says American businesses lose more than 100,000 million dollars a year because of tired workers. Some employees are too tired to report for work. They have accidents or are less productive at work. Other costs included increased visits to doctors.
Many experts say a good amount of sleep is as important to health as diet end exercise. They say most people need 7 to 9 hours of sleep each night. Less than that can interfere with mental and physical abilities. It can lead to more serious problems, including severe sleeplessness.
Researchers involved in the study axe suggesting a number of steps to help prevent sleep disorders. They suggest a campaign to inform. the public about the problem. They want increased education and training among health care workers. And they are calling for new technology to identify and care sleep problems.
Which of the following problems was not mentioned in the study？
(30)

A. The reason that people need sleep.
B. The results of sleep loss.
C. The effects of oversleeping.
Different kinds of sleep disorders.