4) a question with more than one answer! :D
I believe because it falls across multiple lines without obvious breaks. The line breaks are important because the first word of each line gets emphasis.
Echo is on hand to stall Hera with mindless chatter so that Zeus can escape. But when Hera realizes that she's being played, she's not psyched. As a punishment, Her a takes away Echo's voice so that she is only able to repeat whatever she hears. Like, say, hearing your own echo in a canyon.