Consider the following method:

public void v$($String a$[])\{$

for$($int i $=0$; i $<$ a$.$length; i$++)\{$

a$[$i$]=$ reverse$($a$[$i$])$;

$\}$

$\}$

Assume that the method reverse$()$ has a time complexity of O$($n$).$ If we use the active operation approach to determine the time complexity of this method, which line should we choose as the active operation?