单项选择题
A.12 months
B.24 months
C.48 months
D.60 months
单项选择题 To determine what navigation lights and day-shapes must be displayed on mobile offshore drilling units under tow，you should check the（）.
单项选择题 To determine the number of portable fire extinguishers required on an inspected vessel，you should check the（）.
单项选择题 To determine the number of portable fire extinguishers required on an inspected vessel，you should check the（）.