What is described as a stream of instructions sent by a software application to a processor?

The correct answer is threading.

Threading refers to the capability of a software application to manage multiple sequences of instructions concurrently within a single process. Each "thread" represents a separate path of execution, allowing the application to perform tasks simultaneously or to break a task into smaller, manageable units that can be processed in parallel by the processor. This creates an efficient use of the processor's resources by maximizing the time the processor spends executing commands rather than being idle.

In contrast, multithreading builds upon this concept by allowing multiple threads to be executed in parallel, often leveraging multiple processor cores. While multithreading involves multiple threads, threading itself is the foundational concept that ensures a software application can manage and execute its instructions within a single context.

Symmetric Multiprocessing (SMP) involves the use of two or more processors or cores sharing the same memory and I/O resources, but it does not define the stream of instructions itself. Virtualization refers to creating virtual instances of operating systems or hardware, which is unrelated to the concept of a stream of instructions from an application to a processor.