题目内容：
Questions are based on the following passage.
Baekeland and Hartmann report that the "short sleepers" had been more or less average in their sleepneeds until the men were in their teens．But at about age 15 or so, the men voluntarily began cutting downtheir nightly sleep time because of pressures from school, work, and other activities．These men tended toview their nightly periods of unconsciousness as bothersome interruptions in their daily routines.
In general, these "short sleeps" appeared ambitious, active, energetic, cheerful, conformist (不动摇) intheir opinions, and very sure about their career choices．They often held several jobs at once, or workers full-or part-time while going to school．And many of them had a strong urge to appear "normal" or "acceptable"
to their friends and associates．When asked to recall their dreams, the "short sleepers" did poorly．More than this, they seemed to prefernot remembering．In similar fashion, their usual way of dealing with psychological problems was to deny thatthe problem existed, and then to keep busy in the hope that the trouble would go away.The sleep patterns of the "short sleepers" were similar to, but less extreme than, sleep patterns shown bymany mental patients categorized as manic ( 疯人 ).
The "long sleepers" were quite different indeed．Baekeland and Hartmann report that these young menhad been lengthy sleeps since childhood．They seemed to enjoy their sleep, protected it, and were quiteconcerned when they were occasionally deprived of their desired 9 hours of nightly bed rest．They tended torecall their dreams much better than did the "short sleepers."Many of the "long sleepers" were shy, anxious, introverted ( 内向 ), inhibited ( 压抑 ), passive, mildlydepressed, and unsure of themselves (particularly in social situations)．Several openly states that sleep was anescape from their daily problems.
According to the report, A．many short sleepers need less sleep by nature
B．many short sleepers are obliged to reduce their nightly sleep time because they are busy with their work
C．long sleepers sleep a longer period of time during the day
D．many long sleepers preserve their sleeping habit formed during their childhood
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