单项选择题
A.It is inflated by a small CO2 bottle that is automatically tripped when the front zipper is at the top of the zipper track
B.It is inflated by a small CO2 bottle that is manually tripped
C.It is inflated by blowing through an inflation tube
D.It inflates by seawater bleeding into the inflation bladder and reacting with a chemical
单项选择题 How is the annual rate of change for magnetic variation shown on a pilot chart?（）
单项选择题 How is a safe water mark，that can be passed close aboard on either side，painted and lighted?（）
单项选择题 How does the effect known as “bank suction” act on a single-screw vessel proceeding along a narrow channel?（）