ow does the reverse$\_$str function improve the following program?

def rec$\_$reverse$\_$str$($st$,$ pos$)$:

$"""$

Returns a new string that is the reverse of st

When first called, the pos parameter must be zero

$"""$

if pos $==$ len$($st$)$:

return $""$

return rec$\_$reverse$\_$str$($st$,$ pos$+1)+$ st$[$pos$]$

def reverse$\_$str$($st$)$:

$"""$

Calls recursive reverse$\_$str function with zero for the second parameter

$"""$

return rec$\_$reverse$\_$str$($st$,0)$

Group of answer choices

It allows the user to call reverse$\_$st without having to add the initial $0$ argument.

It reduces the time complexity of the rec$\_$reverse$\_$str function.

It checks to make sure the argument passed to rec$\_$reverse$\_$str is a non$-$empty string.

It adds lines to the program, which looks more professional.