I think it's smart, in Japanese, how they have a discrete sound for a question mark (i.e. ka) rather than relying on inflexion.
um, my Japanese teacher, who is Japanese, would not agree with you. there IS an inflexion in KA. your voice is to go up on KA rather than slowly going up on say, the last two words in an english sentence.
In fact it is pretty close to english sentences as far as inflexion goes. It is considered good form to make the listener aware that you have in fact posed a question by using an inflection. Rude people who are in a hurry don't bother though, just like in America..it's sound more like a statement than a question, which could be the case since most Americans think they know everything anyway and feel the need to answer the question for you. O Genki desu Ka? don't forget to go UP with your inflexion at the end there kids.