单项选择题

接线盒的安装高度是( )

A．距地面0.2m
B．距地面0.3m
C．顶板下0.2m
D．顶板下0.3m

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单项选择题

疲劳实验时，试样承受的载荷为（）
A、交变载荷
B、静载荷
C、冲击载荷
D、无载荷

单项选择题

Which of the following is correct about the haze:

A．The components of haze and fog are basically the same, but haze particles are larger.
B．Haze and fog are both harmful to human health.
C．Haze particles less than 10 microns in diameter are known as respirable particles.
D．Both haze and fog can form secondary particles.
E．No matter the diameter of the particles in haze, they can penetrate to the deep lung.