Fix this error

Which of these lines of codes in the code snippet given below will throw a compilation error?

public class Sample
{
 public static void Main()
 {
 //L1
 int num = 4;
 int A = Square(num);

 //L2
 int B = Square(12);

 //L3
 int C = Square(A * 3);
 }

 static int Square(int i)
 {
 int input = i;
 return input * input;
 }
}

Options

1. Only L1
2. Only L2
3. Only L3
4. All L1, L2 and L3