Which of the following correctly describes turnaround time?

Turnaround time refers to the total time taken for a process to complete its execution from the moment it is submitted until it is fully finished. This encompasses all stages the process goes through within the system, including its waiting time, the time it spends in the ready queue, any time it may spend waiting for hardware or resources, and the actual execution time on the CPU.

This broad definition means that turnaround time captures the complete lifecycle of the process in the operating system, making option A the correct choice. It emphasizes that turnaround time is not limited to just execution or waiting times; rather, it aggregates all the time components that contribute to when the process starts until the point where it completes its execution and the results are produced.

The other options provide narrower definitions that exclude critical components of the total time spent by the process in the system. For instance, some options focus solely on waiting or execution times, failing to account for the entire timeline of the process's lifecycle.