Why is the automatic answerback request (WRU) first used by the CES after an Inmarsat-B TELEX call has been placed from a ship?

Correct Answer: Option A — Identify the SES making the request.

The 'Who Are You' (WRU) signal is a standard TELEX protocol used to trigger an automatic answerback from the remote station. When a ship initiates a call, the CES uses this to verify the identity of the Ship Earth Station (SES) for billing and routing purposes.