How many days a year does a public water system need to regularly serve individuals?

A public water system is required to operate regularly to meet health and safety standards, ensuring that individuals have reliable access to drinking water. The correct choice of 60 days indicates that a water system does not only need to provide service during specific seasons or for limited periods but must maintain a consistent service standard. This duration helps ensure that the system is reliable and that there are measures in place to safeguard public health, particularly in managing water quality and availability.

The other options do not align with the regulatory expectations for public water systems, as they suggest shorter or less frequent operation periods, which would not adequately ensure that customers have access to safe drinking water throughout the year. The 60-day requirement emphasizes the importance of a water system's continual operation to meet public health needs.