Final answer:
A subroutine may refer to a function, subprogram, procedure or method, which are sequences of program instructions that perform a specific task. A variable, on the other hand, is a storage location for data and is not a subroutine.
Step-by-step explanation:
A subroutine may be used to refer to a variety of elements in programming. A subroutine is a sequence of program instructions that performs a specific task, packaged as a unit. This unit can then be used in programs wherever that particular task should be performed. Subroutines can be referred to by several names depending on the programming language and the specific structure and purpose of the subroutine.
- A function is a type of subroutine that returns a value and can be used in expressions.
- A subprogram is a generic term for a sequence of instructions that can be called by other programs or subprograms.
- A procedure, similar to a function, is a type of subroutine that may not return a value and is often used to execute a sequence of statements.
- A method is a subroutine associated with a class or an object in object-oriented programming.
A variable, however, is not a subroutine. A variable is used to store information that can be referenced and manipulated in a computer program. Therefore, when referencing a subroutine, the correct answers from the given options are A) a function, B) a subprogram, C) a procedure, and D) a method.