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【单选题】Questions 62 to 66 are based on the following passage. If a mother pushes her small son in a swing (秋千), giving only a light force each time he returns, eventually he will be swingirg.quite high. The ...
A.
the speed of a motor in revolutions
B.
the frequency at which a motor vibrates
C.
the amplitude of an engine that oscillates
D.
the changes in a dial within a ear engine
【单选题】Riding on the swings (秋千) and (playing) with the ducks in the pond (was) our (children's) greatest pleasure when we took (them) to the park.
A.
playing
B.
was
C.
children's
D.
them