Which of the following best describes a PLC?

A PLC, or Programmable Logic Controller, is best described as a programmable device for automation and safety. This is because PLCs are designed to control industrial processes, machinery, and equipment by using user-defined programs. These programs enable the PLC to respond to inputs from sensors and switches, execute specific operations, and control output devices like motors and actuators.

The versatility of PLCs is key to their role in industrial automation; they can be programmed to perform a variety of tasks, making them invaluable in many manufacturing and industrial environments. Additionally, PLCs are equipped with safety features and can implement safety protocols to ensure safe operations within the automated systems. This capacity for both automation and safety distinguishes PLCs from simpler analog devices or hardware-only solutions that would lack such programmability and flexibility.

By contrast, options that describe PLCs as simple analog devices or exclusively for monitoring do not encompass their full functionality, while the description of PLCs as hardware-only misses the essential aspect of programmability that is fundamental to their operation.