In this task, you will use your knowledge about language (and common sense) to determine what element the marked number refers to. The numbers are marked with two underlines around them, like: _ number _. Your answer should be chosen from the given text, and should not contain other words.
Q: Peter Bishop: Just tell us what you know about the stations .
Ed Markham: First of all , they 're as old as dirt . They say when Marconi invented the radio , the first thing he heard was the numbers , like they were floating around in space just waiting for someone to listen .
Peter Bishop: You 're trying to tell me that Marconi picked up a transmission before humans invented the technology to send _ one _ ?
A:
transmission