I really hope they don't choose Bitcoin or Ethereum. Something like Stellar XLM is not only environmentally responsible, the protocol settles in seconds rather than minutes.
You don't need fast settlements for most payments (cheaper than a car). Bitcoin (BTC) transactions used to be irreversible (the proof-of-work needed to double-spend was too much for such amounts), until they ruined it by implementing return-by-fee (RBF). Fortunately Bitcoin Cash (BCH) keeps the original implementation, usually less than a second zero-conf transactions and no RBF.