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【判断题】
当挖掘机在高压电缆附近作业时,它们需要保持一定距离,当电压是220伏时,最小安全距离为2米;当电压是500千伏时,最小安全距离为11米A.
正确
B.
错误
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皮皮学刷刷变学霸
举一反三
【简答题】Que les couleurs (ne rien perdre) de leur intensité.
【单选题】If a person's eye has been looking at an object in bright sunlight for some time, and then shifts to an object not well lit--such as a lawn or shrub in shadow--we can expect ______.
A.
a time lag in the focusing ability of the eye
B.
some inability to see colors of the latter-named objects until loss of sensitivity has been regained
C.
the immediate loss of the 'afterimage' of the first object
D.
adaptation in the central area of the eye but little adaptation in the lateral areas to the new intensity level
【单选题】（ ）The main idea of the third paragraph is that．
A.
the mass of the fishDecides the intensity of electric power it generates
B.
the strength of shock givenBy a young electric ray can only light theBulb of apocket flashlight
C.
to make full use of the energy producedBy electric fish，suitable wires shouldBeavailable
D.
a mature torpedo is capable of producing enough electricity to knockDown a man
【单选题】In spite of the treatment, the pain in his leg grew in ______ .
A.
gravity
B.
extent
C.
intensity
D.
amount
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