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 sea water bleeding into the flotation bladder and reacting with a chemical therein