What does 'datum' mean in a search and rescue context, and why does it typically need to be updated as a search continues?

A. Datum is a fixed geographic reference that never changes once a search begins

B. Datum is calculated once by the MRCC and never affects the on-scene vessel's own search execution

C. Datum refers only to the chart's horizontal reference system (e.g. WGS84), unrelated to search planning

D. Datum is the most probable position of the search object at a given time, calculated from the last known position adjusted for the estimated effect of drift (wind and current acting on the object) — because drift continues throughout the search, the datum must be recalculated periodically, or a later search leg will be searching where the object used to be, not where it now is

A. Nothing — a test lift can proceed immediately after repairs

B. The area within the grab's swing radius should be cleared of personnel before the lift

C. Testing should wait until cargo operations begin

D. Only the crane operator needs to be aware the lift is happening

A. Only the weather forecast for the next watch

B. The lunch schedule for the deck team

C. Who must remain clear of the exclusion zone while the lift takes place

D. The cargo manifest for the next port