Not quite true. Often, when asking a question requiring an opposing answer, the question takes the form of a statement followed by a question mark. You're not going to the concert? Yes, I am! You sang with the Beatles? No, I didn't! In normal, everyday English, it is also very common to ask a question just by inflection, rather than reversing subject-verb order. She's taking the train to Paris? Yes, the bus takes too long.