To troubleshoot poor fusion at the base metal when TIG welding a stainless steel butt joint, which step is essential?

• A. Increase root gap and apply more filler
• B. Adjust heat input and travel speed; ensure filler metal compatibility
• C. Verify joint cleanliness, oxide removal, shielding gas coverage, heat input, and compatible filler metal.
• D. Ignore shielding gas and rely on ambient air.

Answer: (C)