What fitting on the mast works in conjunction with the shrouds to control side bend of the mast?（）

A.Cutting off the bitter and towing ends of the wire rope
B.Splicing two wire ropes together
C.Removing the wire rope from the drum and reversing it so that the towing end becomes the bitter end
D.Removing the wire rope from the drum and turning it over so that the wire bends in the opposite direction when rolled on a drum

A.Flame safety lamp
B.Combustible gas indicator
C.Oxygen indicator
D.H₂S meter

A.A black ball that is hoisted when the ship anchors
B.A buoy attached to the anchor
C.A buoy attached to the scope of an anchor chain
D.A mark of the number of fathoms in an anchor chain