In small-angle stability，when external forces exist，the buoyant force is assumed to act vertically upwards through the center of buoyancy and through the（）.

A.center of gravity
B.metacenter
C.center of flotation
D.keel

A.uncorrected KG
B.virtual height of the center of gravity
C.metacenter
D.metacentric height

A.uncorrected KG
B.maximum allowed KG
C.virtual height of the center of gravity
D.metacentric height