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 therei