单项选择题
A.one fixed power pump and one portable hand pump
B.one fixed hand pump and one portable hand pump
C.two portable hand pumps
D.either "A" or "B"
单项选择题 For optimum stability during jacking operations，mat ballast tanks or spud cans should be（）.
单项选择题 For means of abandonment of a ship，which type of embarkation does not require prior approval by the Coast Guard?（）
单项选择题 For H2S detection，sensitized tapes indicate H2S presence by means of discoloration of an exposed spot on the tape. The shade of the color on the spot depends upon the concentration of H2S and（）.