According to the passage，"span"means______．
A. longevity
B. a length of time
C. a long period of time
D. a long distance from one place to another
Scientists think that the difference between animals and man is______．
A. animals cannot learn
B. animals cannot speak
C. animals cannot think like us
D. animals do not have their own language
In order to live longer______．
A. we have to try to be on a diet
B. we shouldkeep inhigh spirits
C. we should trV to do more exercise
D. we should postpone the process of aging
In 2006, she was elected ______ chairman of the Student Union.
A. an
B. a
C. \
D. the
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