When accomplishing welding repairs with an electric arc welding process, what is generally the cause of slag inclusion when welding a single-V butt joint?

Correct Answer: Option C — The weld was performed with inadequate cleaning between passes.

Slag inclusion in a single-V butt joint is typically caused by inadequate cleaning between weld passes. If slag from a previous pass is not removed, it becomes trapped under the subsequent layer, creating a weak point in the weld metal that reduces the joint's overall tensile strength.