On May 23,1989，Stefania Follini came out from a cave at Carlsbad，New Mexico.She hadn't
seen the sun for eighteen and a half weeks.Stefania was in a research program，and the scientists in
the program were studying body rhythms(節(jié)奏). In this experiment Stefania had spent 130 days in a
cave,30 feet in depth.
     During her time in the cave，Stefania had been completely alone except for two white mice.Her
living place had been very comfortable，but there had been nothing to tell her the time.She'd had no
clocks or watches，no television or radio.There had been no natural light and the temperature had
always been kept at 21℃.
     The results were very interesting.Stefania had been in the cave for over four months，but she
thought she had been there for only two.Her body clock had changed.She hadn't kept to a 24hour day，
she had stayed awake for 20～25 hours and then had slept for 10 hours.She had eaten fewer meals and
had lost 171 bs in weight as a result！She had also become rather depressed(抑郁).
     How had she spent her time in the cave？As part of the experiment she'd done some physical and
mental tests.She'd recorded her daily activities and the results of the tests on a computer.This computer
had been specially programmed for the project.Whenever she was free，she'd played cards，read
books and listened to music.She'd also learned French from tapes.
      The experiment showed that our body clocks are affected by light and temperature.For example，
the pattern of day and night makes us wake up and go to sleep.However，people are affected in
different ways.Some people wake up naturally at 5：00 am，but others don't start to wake up till
9：00 or 10：00 am.This affects the whole daily rhythm.As a result，the early risers are at their best
in the late morning.The late risers, on the other hand，are tired during the day and only come to life in
the afternoon or evening!

1. Stefania stayed in the cave for a long time because________.

A. she was asked to do research on mice
B. she wanted to experience loneliness
C. she was the subject of a study
D. she needed to record her life

2. What is a cause for the change of Stefania's body clock?

A. Eating fewer meals.
B. Having more hours of sleep.
C. Lacking physical exercise.
D. Getting no natural light.

3. Where does the text probably come from ?

A. A novel.  
B. A news story.
C. A pet magazine.  
D. A travel guide.