Understand the concept of excludability: An excludable good is one where it is possible to prevent people who have not paid for it from having access to it.
Analyze each option: Determine whether each option can be restricted to only those who pay for it.
Consider 'The court system': This is a public service that is generally available to everyone, regardless of payment, so it is non-excludable.
Consider 'The public road': Public roads are typically available for use by everyone, making them non-excludable.
Consider 'MP3 Downloads': These can be restricted to only those who purchase them, making them excludable.