In stopping distances of vessels，head reach can best be described as the ______.
A.difference between the vessel's speed through the water at any instant and the new speed ordered on the telegraph
B.distance the vessel has actually run through the water since a change of speed was ordered
C.distance the vessel will run between taking action to stop her and being stationary in the water
D.speed at which a vessel should proceed to ensure that she will run a predetermined distance，once her engines have been stopped
正确答案是C