Re: Instead of foul language?
Hi and welcome to the forums.
You can just say "What IS this?" with the emphasis on "is." You don't need to say "What the *** is this?" If you really need to be emphatic, What the hell is this or What the heck is this, if you want to avoid the very mildly offensive "hell." There are so many: What on God's green earth is this? What in the name of all that's holy is this? What in heaven's name is this? What in the world is this? Good lord, what IS this?
Damn (still offensive to some, but not many)
Or you can be really creative and make your own up.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.