A figure eight knot is used to（）.

A.rot
B.shrink
C.stretch
D.unlay

A.deck fitting used to secure mooring lines
B.casting fitted at the side of a weather deck，used as a fairlead
C.sharp block of wood used to support hygroscopic cargo
D.smoke pipe for the galley stove

A.strengthen the line
B.increase its efficiency
C.prevent hand injury by covering loose ends
D.make the line more flexible