What chain is Rio on?

Excuse me, could you please clarify which specific "Rio" you are referring to in this context? Are you asking about a particular blockchain platform, a cryptocurrency project, or perhaps a technology or service related to the blockchain industry? Without further context, it's difficult to give a precise answer. However, if you're asking about a cryptocurrency project or blockchain platform named Rio, it would be helpful to know more about the specifics of this project, such as its purpose, use case, or any distinguishing features. With this information, I may be able to provide a more accurate answer to your question.