According to CSA W47.1, a Class V Welder is permitted to weld:

A Class V Welder, as defined by CSA W47.1, is qualified to weld in all positions. This classification indicates that the welder possesses the skills and knowledge necessary to perform welding tasks not just in a restrictive manner but across various orientations including flat, horizontal, vertical, and overhead.

Welding in all positions is particularly significant in industry as it denotes flexibility and capability to handle diverse welding scenarios, which could be encountered on different job sites. Given that Class V credentials cover a broader range of welding positions, it reflects a higher level of proficiency and adaptability compared to lower classifications that might limit the welder to specific orientations only.

Thus, the selection that states a welder is permitted to work in flat, horizontal, and vertical positions captures the essence of a Class V Welder's qualifications, affirming their competency in a variety of welding challenges presented in real-world applications.