What action must the Foreman take after clearing an interlocking or CP on Line 3 of their Form D?

The Foreman is required to report clear at all interlockings and Controlled Points after clearing them. This action ensures that the dispatcher and other relevant personnel are aware of the status of the track and train movements. By providing this information, the Foreman helps maintain safety and operational efficiency on the railway.

Reporting clear at each interlocking and Controlled Point allows for proper tracking of the train's progress and alerts others that the section is safe for subsequent movements. This step is crucial in ensuring that there are no misunderstandings or conflicts in train movements, which could lead to unsafe situations.

The other options do not encompass the necessary actions required by the Foreman in this context. For instance, simply reporting clear at the next station may not provide the comprehensive communication needed across all interlockings and Controlled Points. Waiting for a follow-up train does not apply to the immediate need for communication of clear status, and authentication to the dispatcher might be relevant in other scenarios but does not align with the specific action required upon clearing the interlocking or Controlled Point.