Class Stonewt is declared as follows. 
class Stonewt
{
   //some members
public:
    Stonewt(double lbs);
    Stonewt(int stn, double lbs);
    Stonewt();
    ~Stonewt();
    operator int() const;
    operator double() const;
};
Which function will be invoked by the following line of code ?
wt = 120.0; //wt is an object of type Stonewt

A． Stonewt(double lbs);
B． Stonewt();
C． operator int() const;
D． operator double() const;