Which one of the following CANNOT impart linear motion in a CNC machine?

The correct answer is Chain and sprocket.

Let us analyze the function of each component in the context of imparting linear motion within a CNC (Computer Numerical Control) machine:
1. Linear Motor: Linear motors directly generate linear force and motion along a track without the need for mechanical transmission systems (like screws or gears). They are widely used in high-speed, high-precision CNC machines for direct linear positioning.
2. Lead Screw (and Ball Screw): A lead screw (or ball screw) is a classic mechanical device used to convert the rotary motion of a servo or stepper motor into precise linear motion. It is the most common drive mechanism for CNC axes.
3. Chain and Sprocket: A chain and sprocket drive is designed to transmit rotary motion and torque between parallel shafts. Because of inherent limitations such as significant backlash, chordal action, elasticity, and lack of positioning precision, it cannot be used to impart the accurate, rigid linear motion required for CNC machine tool axes.