单项选择题
By using previous communication system, rescue is often a matter of chance. What does “a matter of chance” mean?（）
A.occasionally B.accidentally C.often D.usually
单项选择题 We（）a sharp lookout while sailing in the iced waters.
单项选择题 When a mis-entry（）in the logbook, a red line would be drawn through that part.
单项选择题 （）, which consisted of seven short blasts and one prolonged blast, all passengers have to go to their assembly station.
