Which scenario best demonstrates pass-by-reference behavior?

• A. A function returns a modified copy of a value without changing the original
• B. A function can modify the original object passed in
• C. A function always returns a new object
• D. A function reads data without modifying it

Answer: (B)

Pass-by-reference means the function receives access to the actual object provided by the caller, not a separate copy. When the function changes the object’s internal state, those changes are visible to the caller once the function returns. This is exactly what happens when a function can modify the original object passed in—the caller’s data is altered because the function is operating on the same object.

For example, if a function takes a reference or pointer to an object and sets one of its fields, calling it with your variable will reflect that change outside the function. If instead the function worked on a copy, the original would stay unchanged, even though the function returned a modified result. Reading data without modifying it also doesn’t demonstrate pass-by-reference, since no changes to the original occur.