GEAS COACHING PART 3

Which constructor will be called from the object
created in the below C++ code?
class A
{
int I;
A ()
{
i=0; cout&|t;&|t;i;
}
A (int x=0)
{
i=x; cout&|t;&|t;i;
}
};
A obj1;

Which is correct for the class defined below?
class student
{
int marks;
public:student(){}
student(int x)
{
marks=x;
}
};
main()
{
student s1(100);
student s2();
student s3=100;
return 0;
}

Which constructor will be called from the object obj2
in the following C++ program?
class A
{
int I;
A();
{
i=0;
}
A(int x)
{
i=x+1;
}
A(int y, int x)
{
i=x+y;
}
};
Aobj1(10);
Aobj2(10,20);
Aobj3;

Which class/set of classes can illustrate polymorphism
in the following C++ code?
abstract class student
{
public:int marks;
calc_grade();
}
class topper:public student
{
public:calc_grade()
{
return 10;
}
};
class average:public student
{
public:calc_grade()
{
return 20;
}
};
class failed{int marks;};