Which key would be used to indicate the end of a manually dialed number in a telephone, facsimile or data call via an Inmarsat-A SES?

Correct Answer: Option D — #

In Inmarsat-A and similar legacy systems, the # key serves as the standard end-of-selection signal for manually dialed telephone or data calls. This informs the Coast Earth Station that the dialing sequence is complete, allowing the automatic switching equipment to process the connection to the public switched telephone network.