$1.$For this and next question, assume the following code successfully compiles and runs on a modern linux machine $($assume any irrelevant details have been omitted; also assume that all required header files are included$)$:

int main$($int argc, char$**$ argv$)$

$\{$

int a $=0$;

pid$\_$t child$\_$pid;

child$\_$pid $=$ fork$()$;

a$++$;

if$($child$\_$pid $==0)$

$\{$

pid$\_$t grand$\_$child$\_$pid;

grand$\_$child$\_$pid $=$ fork$()$;

a$++$;

$\}$

else

$\{$

a$++$;

$\}$

printf$("$Hello$!$

$")$;

printf$("$a is $\%$d

$",$ a$)$;

wait$($NULL$)$;

return $0$;

$\}$

Assuming fork$()$ never fails, how many times will the message "Hello!

$"$ be displayed?

$1$

$3$

$4$

$2$