When more than one vessel is being assisted by an icebreaker, distances between vessels should be constant. Which signal should be given by a vessel which is ahead of another and whose speed suddenly begins to drop?

A
Four short blast on the whistle
B
A flag hoist consisting of the code figure "4"
C
A flag hoist consisting of the code figure "5"
D
A flag hoist consisting of the code letters "FE" (Foxtrot-Echo)
E