Consider the following mergeSortHelper method, which is part of an algorithm to recursively sort an array of integers.

/** Precondition: (arr. length == 0 or 0 <= from <= to <= arr. length)

* arr. length == temp. length

*/

public static void mergeSortHelper(int[] arr, int from, int to, int[] temp)

{

if (from < to)

{

int middle = (from + to) / 2;

mergeSortHelper(arr, from, middle, temp);

mergeSortHelper(arr, middle + 1, to, temp);

merge(arr, from, middle, to, temp);

}

}

The merge method is used to merge two halves of an array (arr[from] through arr[middle], inclusive, and arr[middle + 1] through arr[to], inclusive) when each half has already been sorted into ascending order. For example, consider the array arr1, which contains the values {1, 3, 5, 7, 2, 4, 6, 8}. The lower half of arr1 is sorted in ascending order (elements arr1[0] through arr1[3], or {1, 3, 5, 7}), as is the upper half of arr1 (elements arr1[4] through arr1[7], or {2, 4, 6, 8}). The array will contain the values {1, 2, 3, 4, 5, 6, 7, 8} after the method call merge(arr1, 0, 3, 7, temp). The array temp is a temporary array declared in the calling program.

Consider the following code segment, which appears in a method in the same class as mergeSortHelper and merge.

int[] arr1 = {9, 1, 3, 5, 4};

int[] temp = new int[arr1.length];

mergeSortHelper(arr1, 0, arr1.length - 1, temp);

Which of the following represents the arrays merged the first time the merge method is executed as a result of the code segment above?

A. {9} and {1} are merged to form {1, 9}.
B. {1, 9} and {3} are merged to form {1, 3, 9}.
C. {1, 9} and {5, 4} are merged to form {1, 4, 5, 9}.
D. {1, 3, 9} and {5} are merged to form {1, 3, 5, 9}.
E. {1, 3, 9} and {4, 5} are merged to form {1, 3, 4, 5, 9}.