Which of the following instructions allows a second program to execute simultaneously with the current program?

The instruction that allows a second program to execute simultaneously with the current program is appropriately identified as the RUN instruction. This command is used to initiate the concurrent running of another program without interrupting the current execution. It is particularly useful in complex operations where multiple tasks must be performed in parallel for efficiency, such as in multitasking or when managing a series of coordinated workflows.

By leveraging the RUN instruction, operators can enhance productivity by allowing different parts of a machine or process to operate at the same time, rather than sequentially. This capability is critical in modern numerical control systems, where simultaneous processes can lead to more effective use of resources and time.