On a ship，when may a work vest be substituted for a required life preserver?（）

Recharging a previously used cartridge-operated dry-chemical extinguisher is accomplished by（）.

Shipping society approved buoyant work vests are considered to be items of safety equipment and may be worn by members of the crew（）.

Radiation spreads a fire by（）.

On a ship，watertight doors should be operated（）.

The discharge side of every fire pump must be equipped with a（）.

Portable foam type fire extinguishers are most effective on（）.

One of the limitations of foam as an extinguishing agent is that foam（）.

Since the fire is increasing on board the vessel，the Captain orders that the ship be（）.

The brickwork surrounding the firebox of a boiler is known as（）.