Which of the following inspectors can qualify a welder?

A certified welding inspector is the correct choice because they possess specific training and credentials that enable them to evaluate a welder's skills and ensure compliance with the necessary standards and specifications. Certified welding inspectors are knowledgeable about welding processes, procedures, and codes, which is essential for assessing the quality of welds and the performance of welders. Their certification signifies a recognized level of expertise that is critical for maintaining safety and quality in pipeline construction and maintenance.

On the other hand, while a company representative may have some understanding of welding, they may lack the formal qualifications needed to qualify a welder. A senior engineer, while possibly knowledgeable about engineering principles, may not have the specialized training in welding inspection. An untrained supervisor would not have the required expertise to assess welder qualifications accurately. Thus, the integrity of the qualification process is upheld through the role of a certified welding inspector.