Which of the lathe operations listed is best done with the carriage locked in position?

Correct Answer: Option A — Facing work held in a chuck.

Facing operations require the tool to move perpendicular to the axis of rotation. Locking the carriage ensures the cross-slide maintains a precise, rigid path across the face of the workpiece, preventing unwanted longitudinal movement that would result in an uneven or tapered surface finish during the machining process.