单项选择题
A.every two years
B.every three years
C.every year
D.every four years
单项选择题 Having studied the INMARSAT document, GMDSS document, SOLAS Convention and other international navigation documents, we all know that the Chapter IV of SOLAS Convention is mainly about（）.
单项选择题 Stations are grouped by countries arranged in the（）order of their country symbols.
单项选择题 When engaged on international voyages, ships of 1600 tons gross tonnage and upwards shall be fitted with a（）.