You should really make more options for the answers. This is why easy questions are being missed, not because we don't know the answer but rather because we don't know how you want it phrased. For example, I tried typing "assassination of Franz Ferdinand" and it wasn't accepted. I would recommend allowing any answer containing "Franz Ferdinand" to be accepted in order to prevent this. "October Revolution" should also be accepted for Bolshevik Revolution. Personally, I would even accept "Russian Civil War". Good quiz, just a few pointers to make it work better.