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参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
【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.
if the engine moves too fast
B.
if the engine’s amplitude increases
C.
if a tire gets out of balance
D.
if damage occurs in the engine
【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