Which of the following is true?（）

A.A company should develop a SMS and implement it
B.A company implementing a SMS properly may obtain a DOC
C.Once a company obtains its DOC, each vessel of this company will obtain a SMC
D.DOC is valid for 60 months unless “major non-conformity” is found

A.Passenger ships and high-speed crafts of 500 gross tons or more
B.Oil tankers and Chemical tankers and Gas carriers
C.Bulk freight vessels
D.General cargo vessels

A.It aims to ensure safety at sea
B.It aims to avoid damage to the environment
C.It aims to prevent human injury or loss of life
D.It aims to provide a method to run a company