Answer:
The formal one is "Adiós, señor" . Informal "Hasta luego, Paco. Chao" (I am a native Spanish speaker )
Explanation:
You use "Hasta luego, Paco. Chao" to say goodbye in a jokey way, whereas "Adiós, señor" is to set more distance between you and the other person, is formal.
Hope this helps you!
Estrella (c) tiene mas sentido (makes the most sense)
