Are the threads on oxygen and acetylene hoses the same?

The reason the correct option states that the threads on oxygen and acetylene hoses are not the same is primarily due to safety and compatibility standards within the welding industry. Oxygen and acetylene, as gases used for welding, have distinct properties and requirements for handling.

To ensure safety and prevent the accidental interchange of hoses, which could lead to explosive reactions or inadequate gas flow, the threading on the fittings for oxygen and acetylene hoses is designed differently. Typically, oxygen fittings are right-hand threaded while acetylene fittings are left-hand threaded. This threading standardization helps in preventing incorrect connections, thereby enhancing safety during welding operations.

The other options suggest scenarios where threads might be considered the same, but these do not hold true under standard practices. Each gas requires specific fittings, and adhering to these specific designations is crucial for proper equipment use and safety in welding applications.