Final answer:
If torch operation is to be discontinued, the torch valve must be closed and the gas supply to the torch must be completely shut.
Step-by-step explanation:
The correct answer is option “B”. If torch operation is to be discontinued for a period of “indefinite duration”, the torch valve must be closed and the gas supply to the torch must be completely shut.
This is because keeping the valve open or leaving the gas supply open can pose safety risks such as gas leaks or fires. It is important to switch off the gas supply when not in use to prevent any accidents or hazards.
The correct answer is option not specified since the information provided does not state an exact period of time required to close the torch valve and shut off the gas supply.
However, in general practice for safety, if torch operation is to be discontinued for an extended period, typically more than a few minutes, the torch valve should be closed and the gas supply to the torch must be completely shut off to prevent any potential hazards such as leaks or accidental ignition.
In the context of the given information where a gas spontaneously becomes evenly distributed between two flasks, it is possibly an example illustrating the principle of gas expansion or diffusion, but this does not relate directly to the safety procedures for discontinuing torch operation.
Always adhere to the specific safety guidelines provided by the equipment manufacturer or the policies of the work environment for the correct procedures.