Final answer:
A long-term scheduler a. selects processes from the pool of incoming processes to be admitted into the ready queue and controls the degree of multiprogramming within the system.
Step-by-step explanation:
A long-term scheduler is a component of the operating system that is responsible for deciding which processes are to be admitted from the pool of incoming processes into the ready queue. It effectively controls the degree of multiprogramming, which is the number of processes in memory. The correct answer to what a long-term scheduler is: a) It selects which process has to be brought into the ready queue. The long-term scheduler makes decisions less frequently than the short-term scheduler, which selects processes for CPU allocation, and the medium-term scheduler, which performs the swapping function, removing processes from memory to reduce the degree of multiprogramming.
A long-term scheduler, also known as the admission scheduler, is responsible for selecting which process should be brought into the ready queue. It decides which processes from the job queue should be loaded into the main memory for execution.
This selection process is based on various criteria such as priority, memory requirements, and expected execution time.
Once a process is selected by the long-term scheduler, it is then moved to the ready queue, where the short-term scheduler or CPU scheduler decides which process should be executed next and allocates the CPU to that process.