Which type of manifest would contain real-time updates regarding passenger boarding?

The correct choice is the digital manifest, as it is designed to provide real-time updates and is often integrated with technology that allows for immediate tracking and changes as they occur. In a digital manifest, any updates regarding passenger boarding, such as when passengers check in or change their plans, can be instantly reflected in the system. This flexibility and immediacy help the railroad operator manage capacity and address any issues that may arise during boarding.

In contrast, a static manifest does not account for changes after it is generated; it reflects information at one point in time. A paper manifest shares characteristics with a static manifest, often being compiled and printed without the ability to quickly incorporate changes. Historical manifests contain past data and do not serve the purpose of providing current boarding updates. Thus, the distinct feature of the digital manifest is its ability to provide ongoing and real-time information, making it the most suitable choice for tracking passenger boarding efficiently.