单项选择题
A.在进入封闭舱室之前，戴上氧气面罩。
B.在进入封闭舱室之前，戴上呼吸阀。
C.在进入封闭舱室之前，戴上透气孔。
D.在进入机舱室之前，戴上氧气面罩。
单项选择题 For the duties assigned in the muster list, one person may do more than one work and one work may be done by more than one person.（）
单项选择题 The signals that will be used for emergency should be clearly set out.（）
单项选择题 The muster list may be supplemented by individual cards issued to each member of the crew.（）