Which key is used to indicate the end of a selection in a TELEX call via an Inmarsat-B SES?

Correct Answer: Option C — +

In Inmarsat-B TELEX operations, the + sign is the internationally recognized end-of-selection character. Unlike telephone calls which often use the # key, TELEX protocols require the plus sign to signal the Coast Earth Station that the destination address is complete and the message transmission or connection can proceed.