Mostly a good quiz but.....I think that the clue for "R" is inane. There is no logical distinction between a big city and a little city. I suggest that you think of a different question.
What does the question "One of the main beer ingredients" has to do with geography? It's obviuosly about food. At least rephrase it to something like "US is the biggest supplier of this beer ingredient".
And X? How about the chinese city Xian?