Consider the algebra of lists where,

isEmpty$()=$ True

isEmptyL$($cons$($x$,$L$))=$ False

head$($cons$($x$,$L$))=$ x

tail$($cons$($x$,$L$))=$ L

Let us define the following function,

mystery$($L$)=$ if isEmptyL$($L$)$ then L else cat$($mystery$($tail$($L$)),$head$($L$))$ where we define$$cat as$,$

cat$($s$,$t$)=$ if isEmptyL$($s$)$ then$$t else cons$($head$($s$),$cat$($tail$($s$),$t$))$

What function does$$mystery implement?

Group of answer choices

Make a stack from L

Length of L

Reverse L

Make a nested list of lists from elements of L