What code may be filled in the blank without causing syntax or runtime errors:

public class Test $\{$

java.util.Date date;

public static void main$($String$[]$ args$)\{$

Test test $=$ new Test$()$;

You should add the static keyword in the place of $?$ in Line $\_\_\_\_\_\_\_\_$ in the following code:

Line $1$ public class Test $\{$

Line $2$ private int age;

Line $3$

Line $4$ public $?$ int square$($int n$)\{$

Line $5$ return n $*$ n;

Line $6\}$

Line $7$

Line $8$ public $?$ int getAge$()\{$

Line $9$ return age;

Line $10\}$

Line $11\}$

A$.$ in line $4$

B$.$ in line $8$

C$.$ in both line $4$ and line $8$

D$.$ none