Final answer:
The CRT monitor is not a basic component of a PLC system; while used for monitoring, it's not integral to PLC operation.
Step-by-step explanation:
The PLC, or Programmable Logic Controller, is an essential component in modern industrial automation systems. It's used to control machinery and processes in a wide range of industrial settings. A basic PLC system typically includes the following components:
- Processor: This is the brain of the PLC, executing control instructions programmed by the user.
- I/O system: Input/Output system is critical for interfacing with sensors and actuators in the field, allowing the PLC to monitor and control various devices.
- Power supply: This component provides the necessary power for the PLC and its associated devices to operate.
The option 'CRT monitor' is not a basic component of a PLC system. While a CRT monitor may be used as an interface for monitoring the PLC's operation, it is not integral to the PLC's fundamental operation. Therefore, the answer would be D. CRT monitor.