Correct Answer : Option (C) : direct current with straight polarity is used
Explanation : Direct current with straight polarity (DCEN) is used when TIG welding copper alloys, the electrode is positive and the workpiece is negative. This polarity is preferred when welding copper alloys because it creates a stable arc with a deep and concentrated heat at the point of contact between the electrode and the workpiece, which helps to achieve a consistent weld.
