What does the following Code Snippet do $?$

public static int testArray$($int$[]$ arr, int index$)\{$

if $($index $<0)\{$

return $0$;

$\}$

return arr$[$index$]+$ testArray$($arr$,$ index $-1)$;

$\}$

Group of answer choices

Count the array elements in an integer array:

Concatenate the Array Values

calculate the sum of all elements in an integer array: