Which one of the following repair will cost the least cost?（）

A.Because it is difficult to plan and manage
B.Because it is cannot be well categorized
C.Because it is a difficult work for people to undergo
D.Because it is seldom researched by research

A.inform the chief engineer whenever there are problems
B.reduce the time wasted on checking items
C.know who is responsible for the domestic cleaning equipment
D.know the chain of authority on the ship