Final answer:
Gas cylinder manifolds must activate a local signal and also send an alert to master alarm panels to indicate header changeover, making the correct answer B) local; master.
Step-by-step explanation:
The question is related to the alarm systems associated with gas cylinder manifolds in a laboratory or industrial setting. When a gas cylinder manifold switches from one header (the collection of connected cylinders) to another due to depletion of the first, it is crucial for safety and operational continuity to signal this change.
The correct answer to the student's question is: Manifolds for gas cylinders shall actuate a local signal and shall activate an indicator at all master alarm panels to indicate when or just before changeover from one header to the other. Therefore, the correct choice is B) local ; master.
This ensures that personnel in the immediate vicinity (local signal) are alerted to the change, and that the status change is communicated to central monitoring locations (master alarm panels).