How is the external flotation bladder of an immersion suit inflated?（）
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