单项选择题
(A)163mm (B)440mm (C)6000mm (D)7500mm
(A)梯磴 (B)拉绳 (C)滑轮 (D)升降装置
(A)50Pa (B)100Pa (C)150Pa (D)200Pa
(A)1% (B)5% (C)7% (D)9%
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