Q1:

What will be the output of the program?

#include<stdio.h>
int main()
{
    int i=2;
    int j = i + (1, 2, 3, 4, 5);
    printf('%d\n', j);
    return 0;
}

Because, comma operator used in the expression i (1, 2, 3, 4, 5). The comma operator has left-right associativity. The left operand is always evaluated first, and the result of evaluation is discarded before the right operand is evaluated. In this expression 5 is the right most operand, hence after evaluating expression (1, 2, 3, 4, 5) the result is 5, which on adding to i results into 7.