I've just read the following sentence in a book:
I wonder what that's for?
So is that correct order of words "that" and "is"? In my opinion there should be:
I wonder what's that for?
Am I right? Or might it be both variants are possible?
It should be written this way:
I wonder what that's for.
or
"I wonder, 'What's that for?'"
The first one is a statement and "what that's for" is the subordinate clause; therefore, it's not actually posing a question. The second one with a question mark and quotations is someone thinking out loud. He's questioning what that is for by asking himself the question, "What is that for?"
I hope that might have helped you out. Take care and good luck.