Which task type has no priority and is interrupted by others?

The correct choice highlights a continuous task, which is a type of task that operates in an ongoing manner without being governed by specific timing constraints. Continuous tasks run continuously and can be preempted or interrupted by higher-priority tasks. This characteristic is key in systems where multiple tasks are executed simultaneously, ensuring that critical tasks can interrupt non-critical ones to maintain system responsiveness and performance.

In a control system, continuous tasks are essential for processes that need constant monitoring and adjustments, such as maintaining temperature in a furnace or pressure levels in a pipeline. These tasks typically do not have priority levels assigned to them, making them vulnerable to interruptions when other tasks with higher priorities, such as event-driven or emergency tasks, require immediate attention. This flexibility allows the system to respond quickly to changing conditions or critical events, ensuring safety and reliability.

Understanding the behavior of continuous tasks is crucial, as they often serve as the foundation for monitoring and controlling various processes within a PLC application. Therefore, the nature of continuous tasks and their interaction with other task types is fundamental to developing effective and efficient control strategies in automation.