In an automatic scanning immersion unit, the bridge or carriage serves to:

• A. Control vertical and angular positioning of the scanner tube
• B. Raise and lower the transducer
• C. Support the manipulator and scanner tube and to move it about transversely and longitudinally
• D. Control the angular and transverse positioning of the scanner tube

Answer: (C)

The bridge or carriage is the moving framework that literally carries the scanner assembly. Its main job is to support the manipulator and the scanner tube and to move them across the part in two directions: transversely (side to side) and longitudinally (along the length). This setup lets the automatic immersion unit sweep the area evenly and cover the weld or surface being inspected.

Vertical positioning and angular tilt are handled by other parts of the system, not by the bridge. The bridge focuses on providing the two-axis support and motion needed for scanning, while separate mechanisms manage lifting or tilting as required.