Conventional anchors are least likely to hold in a bottom consisting of（）.

A.in many places a counter current flows in opposition to the main current close to the bank
B.current can vary with depth of water and large deep draught ships can experience different current effects at differing parts of the hull tend to turn to the wind
C.as speed is reduced，the increased proportion of the ship's vector which is attributable to current will set the ship close to obstructions
D.when close to the berth in a head current，there is a danger that flow inshore of the ship becomes restricted and the ship is subject to interactive forces

A.the pivot point and point of influence of wind in are not in alignment
B.the pivot point and point of influence of wind in are in alignment
C.the point of influence of wind moves depending on the profile of the ship presented to the wind
D.the ship steams slowly in rough seas

A.A safety line attached to a man working over the side
B.Used to measure water depth
C.Used to slow the headway of a barge
D.Used to measure the overhead height of a bridge