If you ask me to prove I have $10,000 of money, available to spend, which of the following would you accept as proof: A) $10,000 of cash. B) Seeing my balance

If you ask me to prove I have $10,000 of money, available to spend, which of the following would you accept as proof: A) $10,000 of cash. B) Seeing my balance at a bank (e.g. entering the bank URL on a device you control, and then watching as I log in and navigate to the statement). C) Proof that a non-bank company owes me $10,000. Most people would only count A and B, because they're perfectly liquid.