Exception Handling - General Questions

Which exception does a failed new throw by default?

What will be the output of the program?

#include <iostream>
#include <string>
#include <exception>
using namespace std;

int main() {
    try {
        throw string("oops");
    } catch (const exception &e) {
        cout << "std" << endl;
    } catch (const string &s) {
        cout << s << endl;
    }
    return 0;
}

What will be the output of the program?

#include <iostream>
using namespace std;
int main() {
    try {
        try { throw 1; }
        catch (int) { cout << "inner "; throw; }
    } catch (int) {
        cout << "outer";
    }
    cout << endl;
    return 0;
}

Which standard exception does vector::at throw for a bad index?

Why should exceptions usually be caught by const reference?