Many mobile payment solutions rely on QR codes. In a transaction, what do the QR codes do$?$

They encrypt the transaction information so that it can be transmitted more securely$.$

They identify the banks that hold the account balances.

They embed the users$$ account information so that it doesn$$t have to be physically put in during transactions, thereby increasing the efficiency for offline transactions.

They provide a social media tool for buyers and sellers to interact, thereby allowing for more marketing and promotions.