单项选择题
Bolts, nuts, split pins, hinges, wheels and stoppers should be frequently （）.
A.checked B.closed C.removed D.cleared
单项选择题 Before opening and closing the hatches, the spaces around the covers, all the parts and the gears should be （）.
单项选择题 The foreman said three （）would come on board to load cargo.
单项选择题 The wire ropes and blocks, or pulleys, on a ship are called （）.
