Is it correct to say this?
Is it gramatically correct to say: I wonder what there could be inside that box?
2 Answers
That is perfectly correct. Some people use a question mark, some use a period as it's not technically a question. It's a statement.
An alternative is "I wonder what could be inside that box" whether a question mark or period is used.
Yes, it is correct, however I don´t believe you need the question mark because you are really making a statement even though it is about doubt.