What is output?

#include

using namespace std;

class School $\{$

public:

School$()$;

static int getNextId$()$;

private:

int id $=0$;

static int nextId;

$\}$;

School::School$()\{$

id $=$ nextId;

nextId $+=1$;

$\}$

int School::getNextId$()\{$

return nextId;

$\}$

int School::nextId $=0$;

int main$()\{$

School$()$;

cout $<<$ School::getNextId$()<<""$;

School$()$;

cout $<<$ School::getNextId$()<<""$;

School$()$;

cout $<<$ School::getNextId$()<<""$;

School$()$;

cout $<<$ School::getNextId$()<<""$;

$\}$

Group of answer choices

$3210$

$0123$

$4321$

$1234$