Study the following code snippet:

#ifndef CAR$\_$H

#define CAR$\_$H

class Car

$\{$

public:

Car$()$;

Car$($double speed$)$;

private:

double speed$1$;

$\}$;

#endif

The above file is saved as "Car.h$".$ The following is the source file.

#include "Car.h$"$

Car::Car$()$

$\{$

speed$1=0$;

$\}$

int main$()$

$\{$

Car c$1(30\mathrm{.}00)$;

return $0$;

$\}$

Which of the following is true about the code snippet?

Question $6$ options:

The definition of the Car class is incomplete because the constructor Car::Car$($double speed$)$ has not been implemented in the source file.

To complete the definition of the Car class, the constructor Car::Car$($double speed$)$ must be implemented in the header file before calling it in the source file.

The main function does not compile because it does not know about the existence of the Car::Car$($double speed$)$ constructor.

The default constructor is used because the Car::Car$($double speed$)$ constructor has not been defined.