The song appearing in the EP, Gold Skies, that reached 21 on "Billboard" was released in what year?
Gold Skies (EP): Gold Skies is the debut extended play (EP) by Dutch DJ and record producer Martin Garrix. Animals (Martin Garrix song): "Animals" is a song by Dutch DJ and record producer Martin Garrix, released as a digital download on 17 June 2013 on iTunes. Animals (Martin Garrix song):  The track was a commercial success, reaching the top ten or topping on a number of electronic music charts, topping singles charts in the United Kingdom and Belgium, and reached number 21 on the United States' "Billboard" Hot 100.
i don't know