When lowering manropes alongside a stage rigged over the side of a vessel，they should be allowed to trail in the water（）.
A.to easily remove the kinks that form in the lines
B.to allow the seamen on the stage to know the direction and strength of the current
C.to provide the seaman something to hold onto if he or she falls from the stage into the water
D.only for short periods of time since they will become waterlogged and be very heavy to pull up
