Preemptive multitasking refers to the operating system's ability to interrupt a running task and allocate the processor to another task. In this type of multitasking, the operating system decides when a task will be given control to run, based on factors like priority levels, time slices, or event triggers. This allows for efficient utilization of system resources and ensures that all tasks get a fair share of CPU time. The other options mentioned in the question, such as tasks deciding when to give control to another task or tasks running simultaneously until completion, do not accurately describe preemptive multitasking.