Why did Selena Gomez have cuss words in her album when the sun goes down?

She doesn't. All her songs are clean. She a very down to earth pop star and ignore all the rumors of her that are bad, they aren't true.

EDITED

It is known that Selena Gomez has used only one bad Word ever in her song. Read the lyrics of "Hit The Lights" Sung by Selena Gomez and you'll know what the Word is.