MAYBE
Trs:
 { sel(0(), cons(X, Y)) -> X,
  sel(s(X), cons(Y, Z)) -> sel(X, activate(Z)),
                from(X) -> cons(X, n__from(n__s(X))),
                from(X) -> n__from(X),
                   s(X) -> n__s(X),
   activate(n__from(X)) -> from(activate(X)),
      activate(n__s(X)) -> s(activate(X)),
            activate(X) -> X}
 Comment:
  We consider a duplicating trs.
  FAIL:
   Open