Constructors and Destructors - General Questions

What will be the output of the program?

#include <iostream>
using namespace std;
class A {
public:
    A() { cout << "1"; }
    A(int) { cout << "2"; }
};
int main() {
    A a, b(5);
    cout << endl;
    return 0;
}

Which constructor takes no arguments?

What will be the output of the program?

#include <iostream>
using namespace std;
class A {
    int id;
public:
    A(int i) : id(i) { cout << "C" << id; }
    ~A() { cout << "D" << id; }
};
int main() {
    A a(1);
    A b(2);
    return 0;
}

How many destructors can a class have?

What will be the output of the program?

#include <iostream>
using namespace std;
class A {
public:
    A() { cout << "A"; }
    ~A() { cout << "a"; }
};
int main() {
    {
        A x;
    }
    cout << "M" << endl;
    return 0;
}