Consider the following class definitions:class bClass{public:void set(double a, double b);//Postcondition: x = a; y = b;void print() const;bClass();//Postcondition: x = 0; y = 0;bClass(double a, double b);//Postcondition: x = a; y = b;private:double x;double y;};class dClass: public bClass{public:void set(double a, double b, double c);//Postcondition: x = a; y = b; z = c;void print() const;dClass();//Postcondition: x = 0; y = 0; z = 0 ;dClass(double a, double b, double c);//Postcondition: x = a; y = b; z = c;private:double z;};Which of the following dClass constructor definitions is valid in C++?

A. dClass::dClass(double a, double b, double c)
: bClass()
{
x = a;
y = b;
z = c;
}

B. dClass::dClass(double a, double c)
{
x = a;
z = c;
}

C. dClass::dClass(double a, double b)
: bClass()
{
x = a;
y = b;

}

D. dClass::dClass(double a, double b, double c)
: bClass(a, b)
{
z = c;
}

Answer: D