Answer

Correct Option: (i) Subsystem (also accepted as (ii) Module — sensor is a modular subsystem)

Explanation

Sensor: Device/subsystem that converts physical stimulus (light, force, proximity, temperature) into electrical signal measurable by controller.

• Subsystem: Part of larger robot system that performs sensing.
• Module: Sometimes called sensing module (self-contained).
• Machine: Complete robot or actuator system, not just sensor.
• All the above: Incorrect because sensor alone is not a complete machine.

In robotics hierarchy: Robot System → Subsystems (Sensing, Actuation, Control) → Modules. Sensor belongs to sensing subsystem.

If exam key expects most general, (i) Subsystem (or (ii) Module if they treat module=subsystem). Some keys mark (iv) All the above as sensor can be viewed at any abstraction, but technically Subsystem is precise.

Final Answer

Sensor is a Subsystem (modular sensing unit) → Option (i) (acceptable as (ii) Module).