Answer: c. Visitors can enter the park free of charge and there are always plenty of empty picnic tables
Explanation:
One of the aim of having a park is to accommodate people in large amount, who would come together to have fun individually or in groups depending on personal choices or their purpose for going there. A park would be considered a public good when it's able to accommodate people free of charge and making options for tables for them to hangout, this makes it generally okay for the public.