What is the output of this program?#include <stdio.h> int main() {  int arr[5] = {1, 2, 3,4,5};  int p, q, r;  p = ++arr[1];  q = arr[1]++;  r = arr[p++];  printf("%d, %d, %d", p, q, r);  return 0; }

The output of this program is "3, 2, 4".

Here is the step-by-step explanation:

1. The program declares an integer array arr with 5 elements and initializes it with the values {1, 2, 3, 4, 5}.
2. Three integer variables p, q, and r are declared.
3. p is assigned the value of ++arr[1]. This means that the value of arr[1] is incremented by 1 before being assigned to p. So, p becomes 3.
4. q is assigned the value of arr[1]++. This means that the value of arr[1] is assigned to q and then incremented by 1. So, q becomes 2.
5. r is assigned the value of arr[p++]. This means that the value of arr[p] is assigned to r and then p is incremented by 1. Since p is 3, arr[3] is 4, so r becomes 4.
6. The program prints the values of p, q, and r using the printf function. So, the output is "3, 2, 4".