A system with multiple processors is called a multiprocessing system.
Multitasking is incorrect. Multitasking involves sharing the processor amoung all ready processes. Though it appears to the user that multiple processes are executing at the same time, only one process is running at any point in time.
Multithreading is incorrect. The developer can structure a program as a collection of independent threads to achieve better concurrency. For example, one thread of a program might be performing a calculation while another is waiting for additional input from the user.
“Parallel running” is incorrect. This is not a real term and is just a distraction.
References:
CBK, pp. 315-316 AIO3, pp. 234 -239