The following code is a definition of a class in C$++.$ Which of the following statements is true?

class A $\{$

public:

int a;

A$()\{$ a $=10$; $\}$

$\}$;

A$)$ The class has a parameterless constructor.

B$)$ The class has a destructor.

C$)$ The class has a copy constructor.

D$)$ The class has a default constructor.