单项选择题
If the electronic chart is part of an ECDIS,it must display the minimum data required by IMO/IHO,to include all of the following EXCEPT（）.
A.hydrography B.aids to navigation C.tidal currents D.regulatory boundaries
单项选择题 （）on still water indictes how loading weight distribution affects on longitudinal strength.
单项选择题 ANCHOR HAS ITS OWN CABLE TWISTED AROUND IT defines（）.
单项选择题 （）sends a radio signal from the bottom of the ship to the sea-bed,from which it is reflected.
