Which device provides emergency breathing gas to the diver?

• A. Umbilical
• B. Hard-wire system
• C. Bailout bottle
• D. Non-return valve

Answer: (C)

Emergency breathing gas is supplied by a bailout bottle — a small secondary cylinder carried by the diver that has its own regulator. It provides a standalone, controllable gas source you can switch to if the primary gas or regulator fails, giving you the means to continue breathing and either ascend or reach a safe alternative gas source.

The other options aren’t on-board emergency gas sources: an umbilical is a gas and support line from surface or a support system, not a self-contained backup on the diver; a hard-wire system involves a fixed surface supply, which isn’t portable for an individual’s immediate emergency use; a non-return valve prevents gas from flowing backward in the system, but it doesn’t provide gas itself.