I believe "Ο λόγος" should also be accepted here as a correct answer.
it is 3 years later and ο λόγος is still not accepted. So is that not correct? does it only can be λόγος without "ο"?
Also "ομιλία"? And doesn't "λόγος" mean reason?
Λόγος also mean speech, reason and logic.
Γλώσσα means language or tongue