Umm how about both Houston and Denver. Multiple teams can retire a number for the same person. You should have had multiple team option.
Yes, it's true a 100% sure. Mutombo mentioned this last year when they were talking about if he was going to come back next year. He said Atlanta, Denver and Rockets had vowed to retire him. He also mentioned he hadn't heard from the Sixers yet; the last team he made a serious contribution to (Nets & Knicks are not worth mentioning) Let's hope at least the Rockets and Nuggets keep their word, would be a disgrace if these two would not do it.