单项选择题 When a ship is in summer zone and in seawater of density1025,she must not load to more than the upper edge of the line marked（）.

单项选择题 When a ship is in tropical zone and in seawater of density 1025,she must not load to more than the upper edge of the line marked（）.

单项选择题 A horizontal the 450mm long and 25 mm wide cuts through the loadline disc.It is called the（）.