单项选择题
All dunnage planks and mats must be sent to board（）commencement of loading.
A.prior to B.during C.in the period of D.afterwards
单项选择题 All echo-sounders can measure the（）.
单项选择题 All electrical appliances aboard a vessel should be grounded to（）.
单项选择题 All entries in logbook,（）made,must not be erased or amended.
