单项选择题
A.grooved wheel in a block
B.line to hold a lifeboat next to the embarkation deck
C.partial load of grain
D.sesman's knife
单项选择题 A smooth, tapered pin, usually of wood, used to open up the strands of a rope for splicing is called a (n)（）.
单项选择题 A solution to overcome tripping defects is an arrangement of special plates on either side of the flukes, designed to set them in the correct tripping position. These special plates are called（）.
单项选择题 A spark arrestor（）.