I'm basically looking at sentences which start with a question, and end with an explanation to it. But there may be more instances of a similar structure. Sample sentence :
Can you book a room in advance, because otherwise we'd be in trouble
Should this sentence end with a period or a question mark?
PS: I read the apparently similar question Position of question mark when sentence doesn't end with question but the sentence structure there is different from what I'm looking for.
Edit: I just discovered that this question is a duplicate. A resolved question already exists: Should I use a question mark when the second independent clause of my sentence is not a question?
But i do like the explanations here better.
Best Answer
The usual mantra is 'A parenthetical is deletable without the matrix sentence's syntax, usually expected punctuation [and certainly basic meaning] being compromised'.
Few would object to
but this changes the emphasis from that in the version using the comma. But you could argue that the same punctuation convention should logically apply when the comma is chosen to offset.
Modern styles probably allow even a sentence-medial question mark:
But the use of a sentence fragment is probably less controversial, and quite acceptable as an informal option to many people nowadays: