I was under the impression that có could be omitted if the question allows but not the không? the other "correct" answer is "bạn có một con rắn?" Doesn't that mean "you have a snake" irrespective of the question mark?
If you see someone holding a snake and you speak in astonishing, "You have a snake?" It's more like a demand for confirmation rather than a question. I believe it's the same in every language.
Yeah but I'm not sure if Vietnamese employs upwards inflection to imply the presence of a question. As the language is tonal, if you inflect the word to imply a question, the word itself changes.