B
According to the report by Baekeland and Hartmann, two American authoritative psychotogical research centres, the "short sleepers" had been more or less average in their sleep needs until the men were in their teens．But at about age 15 or so, the men voluntarily began cutting down their nightly sleep time because of pressures from school, work and other activities. These men tended to view their nightly periods of unconsciousness as bothersome interruptions, in their daily routines.
In general, these "short sleeps" appeared ambitious, active, energetic, cheerful,, conformist （循规蹈矩的） in their 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 prefer not remembering．In similar fashion, their usual way of dealing with psychological problems was to deny that the problem existed, and then to keep busy m 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 by many mental patients categorized as manic （疯人）.
The "long sleepers" were quite different indeed．Baekeland and Hartmann report that these young men had been lengthy sleeps since childhood．They seemed to enjoy their sleep, protected it, and were quite concerned when they were occasionally deprived （剥夺） of their desired 9 hours of nightly bed rest．They tended to recall their dreams much better than the "short sleepers．" did．Many of the "long sleepers" were shy, anxious, introverted （内向）, inhibited （压抑） , passive, mildly depressed, and unsure of themselves （particularly in social situations）．Several openly states that sleep was an escape from their daily problems．
50．According to the text, which is probably the writer' s real attitude towards these two living habits ____．
A．both of them are healthy habits  
B．not both of them are unhealthy habits
C．either of them is not unhealthy habits
D．neither of them is healthy habits
51．When sometimes they cannot enjoy adequate sleep, the long sleepers might ____．
A．feel extremely depressed        B．become energetic
C．appeared disturbed         D．feel disappointed
52．The writer implies （暗示） that short sleepers _____ in the text．
A．are ideally vigorous even under the pressures of life
B．often neglect the consequences of inadequate（不足的）sleep
C．do not know how to relax properly
D．are more unlikely to run into mental problems