C#.NET — Functions vs “subroutines” (void methods): ref behavior, recursion, and call rules. Which statements are correct about functions and subroutines used in C#.NET? A function cannot be called from a subroutine. The ref keyword causes arguments to be passed by reference. With ref, changes in the method are reflected back in the caller. A subroutine cannot be called from a function. Functions and subroutines can be called recursively.

Introduction / Context:
This question distinguishes C# method-calling capabilities and pass-by-reference semantics using ref, along with whether recursion is allowed for both value-returning methods (“functions”) and void methods (“subroutines”).

Given Data / Assumptions:

• Five statements mix call rules and ref behavior.
• “Subroutine” is informally used for a void method in C#.

Concept / Approach:
Any method in C# can call any other accessible method, regardless of return type. The ref keyword passes an argument by reference, so assignments in the method affect the caller’s variable. Recursion is permitted for both functions and void methods.

Step-by-Step Solution:

Verification / Alternative check:
Implement small examples: a void Log() calling string GetStamp(); a function int Fib(int n) calling itself recursively; and a ref demonstration where a callee sets a parameter and the caller observes the change.

Why Other Options Are Wrong:

• A includes 1 and 4 (both false).
• C misses statement 2 and adds no contradiction, but it is incomplete.
• D includes 4, which is false.
• E is wrong because a correct grouping exists (2, 3, 5).

Common Pitfalls:
Confusing ref with out, assuming you cannot mix calls between methods that return values and those that do not, or believing recursion is restricted.

Final Answer:
2, 3, 5