What primary feature does Bitcoin's decentralized public ledger provide?

The primary feature of Bitcoin's decentralized public ledger, known as the blockchain, is that it prevents the removal of data once added. This transparency and immutability make the blockchain a reliable record of all transactions. Once a transaction is confirmed and added to the blockchain, it cannot be altered or deleted, which helps ensure the integrity of the data and builds trust among users. This characteristic is crucial for a digital currency system, as it prevents fraud and assures participants that the historical record of transactions is accurate and immutable.

The other possibilities, while they may pertain to aspects of cryptocurrency or payment systems in general, do not accurately describe the main feature of the Bitcoin ledger. For instance, changes to past transactions undermine the integrity of the ledger, which is not permitted. Bitcoin's design does not allow for new monetary policies to be created through its ledger but rather operates independently of governmental monetary systems. Lastly, Bitcoin is known for its price volatility, so it does not guarantee price stability, making this feature not applicable to its decentralized public ledger.