i think all of investors who want to invest in bitcoin is used real money to buy it through exchange site
I think this is not a suitable question to ask. Like you said this is so obvious and this asking person should use his common sense. I think these questions are only for making some posts and then regulating it for a long time. Everyone uses money and everything is bought with this fiat money. This is quite clear and authentic thing that shouldnt be ask at such a platform.