Compare FCAW and GMAW in terms of shielding and slag production.

• A. FCAW can be self-shielded or gas shielded and often produces slag; GMAW uses external shielding gas with little slag.
• B. FCAW uses external shielding gas exclusively; GMAW relies on self-shielding from flux.
• C. GMAW always produces abundant slag; FCAW produces none.
• D. GMAW uses flux-cored wire; FCAW uses solid wire with gas.

Answer: (A)

The key idea is how shielding is provided and whether slag forms during the weld. Flux-cored arc welding uses a flux-filled core in the wire, and it can be self-shielded (no external gas) or gas-shielded (shielding gas from a bottle). The flux creates a protective slag layer on the weld as it solidifies, so slag production is common and usually needs to be chipped away after welding. In contrast, gas metal arc welding uses a solid wire with shielding provided by an external gas source, protecting the weld without relying on flux. This results in little to no slag. So the statement that FCAW can be self-shielded or gas shielded and often produces slag, while GMAW uses external shielding gas with little slag, best captures the differences.