A.400mm B.450mm C.500mm D.550mm
A.350mm B.400mm C.450mm D.500mm
A.10s B.15s C.20s D.25s
A.平板龙骨 B.中内龙骨 C.旁内龙骨 D.船底纵骨
A.磁罗经 B.号钟 C.号旗 D.号灯
