Class declaration Question 1

#include <iostream>

class Sandman
{
public:
    Sandman(int time = 5);
private:
    int time_;
};

Sandman::Sandman(int time) : time_(time)
{
    std::cout << time_;
}

int main()

{
    Which option is incorrect?

    //Sandman firstObj;
    //Sandman firstObj2(10);
    //Sandman();

    // All of the above?

    system("pause");
}