$```$

def f $[$X$]($xs:List$[$X$],$ Ys:List$[$X$])$ : List$[$X$]=$

xs match

case Nil mys

case z :s zs mf $($zs$,$ z :: ys$)$

def g $[$X$]($xs:List$[$X$],$ ys:List$[$X$],$ n:Int$)$ : List$[$X$]=$

def g$2($as:List$[$X$])$ : List$[$X$]=$

as match

case Nil $=>$ if n $<mtext></mtext><mn>0</mn>$ then g$2($ys$)$ else Nil

case z :s zs $\}=>\backslash$mp@subsup$\{$g$\}\{\}\{2\}(\backslash$textrm$\{$zs$\}$

g$2($xs$)$

def h $[$X$]($xs:List$[$X$],$ n:Int$)$ : List$[$X$]=$

if nmathrm$\{$ then

xs

else

val ys $=$ h $($xs$,$ n $-1)$

ys ::: ys

def k $[$X$]($xs:List$[$X$],$ ys:List$[$X$],$ zs:List$[$X$])$ : List$[$X$]=$

xs match

case Nil $=>$ zs

case a :: as $=>($ys$,$ as$,$ a :: zs$)$

$```$

Which of the statements are true:

f is tail$-$recursive $(\backslash (\backslash$mathrm$\{$g$\}2,\backslash$mathrm$\{$~h$\}\backslash ),$ and k are not tail recursive$)$

g $2$ and h are tail$-$recursive $($ f and k are not tail recursive$)$

f and k are tail$-$recursive $($ g $2$ and h are not tail recursive$)$

g $2$ is tail$-$recursive $(\backslash (\backslash$mathrm$\{$f$\},\backslash$mathrm$\{$h$\}\backslash )$ and k are not tail recursive$)$

f$,$ g$2,$ and $\backslash ($ k $\backslash )$ are tail$-$recursive $($ h is not tail recursive$)$