et env be an environment

$\{"$x$"$: NumValue$(25),"$y$"$: NumValue$(30),"$z$"$: NumValue$(40),"$f$"$: Closure$("$x$",$ Plus$($Ident$("$x$"),$Const$(10)),$ env$2)\}$

Suppose we wish to extend env to handle a recursive function call

let rec f $=$ e in $...$

Let env$1$ denote the environment env$1=("$f$","$x$",$ e$,$ env$).$

Which of the following values is obtained when we lookup $"$f$"$ in env$1?$

env$1($x$)$ is undefined since x is the formal argument for the definition of g and is resolved only at its call site.

b$.$

env$1($g$)=$ Closure$($x$,$ e$,$ env$1)$

c$.$

env$1($z$)=$ NumValue$(3\mathrm{.}1415)$

d$.$

env$1($g$)$ is undefined

e$.$

env$1($x$)=$ env$($x$)$

f$.$

env$1($g$)=$ Closure$($x$,$ e$,$ env$)$