单项选择题

The scientist's work was based on______.

A．occasional observations
B．systematic observations
C．observations of several nests
D．observations of an undisturbed nest
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单项选择题
What is the most suitable word that describes the work of a policeman according to the passage
A．Dangerous.
B．Demanding.
C．Distressing.
D．Dramatic.
单项选择题
The organization of the ants has the effect of______.
A．getting the most work done
B．dividing the work up systematically
C．each ant helping with all the tasks
D．each ant doing what it can do best
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