单项选择题
Neglecting friction，you desire to lift a 300 kgs weight with a stress on the hauling part of 100 kgs.Which of the following tackles would you use?（）.
A.Gun tackle B.Luff tackle C.Two-fold tackle D.Double-luff tackle
单项选择题 Manila slings should not be used to load（）.
单项选择题 Manila lines in which the strands are right-hand laid（）.
单项选择题 Limit switches on gravity davits should be tested by（）.
