Regarding Recursion, which part of the following Java Code is considered to be the Base Case?

$1$ public class RangeSum

$2\{$

$3$ public static void main$($String$[]$ args$)$

$4\{$

$5$ int array;

$6$ int start;

$7$ int end;

$8$

$9$ int$[]$ numbers $=\{1,4,3,4,1,8,7,11,9\}$;

$10$ int sum;

$11$ sum $=$ rangeSum$($numbers$,3,7)$;

$12$

$13$ System.out.println$("$Sum $="+$ sum$)$;

$14\}$

$15$

$16$ public static int rangeSum$($int$[]$ array, int start, int end$)$

$17\{$

$18$ if$($start $>$ end$)$

$19$ return $0$;

$20$ else

$21$ return array$[$start$]+$ rangeSum$($array$,$ start $+1,$ end$)$;

$22\}$

$23\}$

Question $18$ options:

a$)$

if$($start $>$ end$)$

$$ return $0$;

b$)$

return array$[$start$]+$ rangeSum$($array$,$ start $+1,$ end$)$;

c$)$

int$[]$ numbers $=\{1,4,3,4,1,8,7,11,9\}$;

d$)$

$$ sum $=$ rangeSum$($numbers$,3,7)$;