What do we use to create a virtual function?

In the given options which is not an Escape sequences 

What value does the scanf("%d %f %c", &a, &b, &c) function return if the user enters 12 12.34 A?

What is the output of the following C program?

int main()

{

  int a[]={1,2,3,4,5};

  printf("%d", a[2]);

}

How many times is 'Abekus' printed on the console?

Which of the following function / types of function cannot have default parameters?

In which of the following a virtual call is resolved at the time of compilation?

Which of the following is the correct syntax of including a user defined header files in C++?

#include <bits/stdc++.h>
using namespace std;

int main()
{
char big_num1[] = "8239206483232728";
long long int num1 = atoll(big_num1);
cout << num1 << "\n";

char big_num2[] = "100000 9 1324100";
long long int num2 = atoll(big_num2);
cout << num2 << "\n";
return 0;
}

Consider the following ANSI C code segment:

z=x + 3 + y->f1 + y->f2;  for (i = 0; i < 200; i = i + 2) {  if (z > i)  {  p = p + x + 3;  q = q + y->f1;  } else  {  p = p + y->f2;  q = q + x + 3;  }  }

Assume that the variable y points to a struct (allocated on the heap) containing two fields f1 and f2, and the local variables x, y, z, p, q, and i are allotted registers. Common sub-expression elimination (CSE) optimization is applied on the code. The number of addition and the dereference operations (of the form y ->f1 or y ->f2) in the optimized code, respectively, are: