Final answer:
The instruction to send program flow out to a subprogram is 'CALL'. It transfers control to the subprogram, pausing the current flow.
Step-by-step explanation:
The instruction that will send program flow out to a subprogram is CALL. When a CALL instruction is executed, the current program flow is paused, and control is transferred to the specified subprogram. This subprogram is often referred to as a function, method, or procedure, depending on the programming language being used. The other options provided, such as JMP/LBL REMARK and SELECT serve different purposes in programming. JMP/LBL (Jump/Label) is typically used for unconditional jumps within the same program. REMARK is used for comments and does not affect the program flow. SELECT is used in decision-making structures to choose among different options or cases, not to call a subprogram.