ML's parametric polymorphism
replyGo lets you constrain type parameters with interfaces. To do anything analagous in SML you have to use functors, which is substantially less convenient. I think people who refer to ML's parametric polymorphism in this context must really be thinking of parametric polymorphism in OCaml or Haskell.
replyYou just do dictionary passing.
replyLike this, you mean? https://haskellforall.com/2012/05/scrap-your-type-classes
replyFine in principle, but AFAIK it never really caught on because the ergonomics suck. Interfaces/traits/type classes do seem to be a popular feature across languages, for what it's worth.