What code fragment should replace $x$ for function $A$ to return the sum of a and $b?$

You may assume that the initial arguments to the function A are positive integers.

function $A(a,b)$

if $x$

return $b$

else

return $A(a-1,b+1)$

end if

end function

$a=b$

$a1$

$b1b=0a$

$b1$

none $of$ the other answers

$b=0b$

$a$

$b1$

none $of$ the other answers

$b=0$