svoid ai_askForUnknownWordTypes(S s) {
  PTElement tree = ai_parseToTreeWithGuessing(s);
  L<S> unknownWords = ai_unknownWordsInSentence(s);
  for (S word : unknownWords) {
    L<PTElement> e = ai_scanParseTreeForWord_all_tighter(tree, word);
    L<S> categories = uniquify(notNulls(mapMethod(e, 'category)));
    if (empty(categories))
      emit("What type of word is " + quote(word) + "?");
    else
      emit("Is " + quote(word) + " " + curlyOpt(textOut_or_orAll_curly(map a(map deAngleBracket(categories)))) + "?");
  }
}