Given the following function:

def reverse$\_$str$($st$,$ pos$=0)$:

$"""$

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

If a user were to call the function like this

reverse$\_$str$("$recursion$")$

What would be the value of pos in the first call?

Group of answer choices

$0$

"recursion"

$1$

Nothing; an error would occur.