The difference between the initial trim and the trim after loading is known as（）.

A.the minimum depth of the river prescribed in the channel maintenance program
B.the edge of a dredged channel
C.the highest level to which the river may rise without flooding
D.the least available water in a channel which limits the draft of boats and tows

A.center of buoyancy
B.center of flotation
C.center of gravity
D.tipping center

A.center of buoyancy
B.center of flotation
C.uncorrected height of the center of gravity of the vessel
D.center of gravity of the vessel corrected for free surface effects