Which of the Following Methods Calculates the Nth Fibonacci Number

Which of the following methods calculates the nth Fibonacci number?

A) public static int method1(int n) {
if (n <= 2)
return 1;
else
return A(n - 1) ;
}
B) public static int method1(String str) {
if(str == null || str.equals("") )
return 0;
else
return 1 + method1(str.substring() ) ;
}
C) private static int method1(int Current, int Previous, int n) {
if (n == 1)
return Current;
else
return method1(Current + Previous, Current, n - 1) ;
}
D) public void method1(Object data) {
if (head == null)
head = new Node(data) ;
else
method1(head, data) ;
}