Today's Geo Quiz introduces us to the woman who, as of today, is the best ranked women's tennis player in the world. We asked you for the hometown of Jelena Jankovic, or "JJ" as she's known.
The city -- and the answer to our Quiz -- is Belgrade, the capital of Serbia.
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The Women's Tennis Association gave Jelena Jankovic the top spot in the sport today. And Jankovic intends to stay there.
â€œHopefully I would like to finish the year as number one ranked player in the world and I will try my best to continue in this way and hopefully I can do it you know there's a couple of tournaments left so I will really work hard and try my best.â€
Working hard is something JJ is used to doing.
"You know this year I struggled a lot with the injuries and I wasn't able to really practise and I wasn't able to produce the tennis that I wanted and now since the US open I haven't had any injuries so I'm every day real spending a lot of time on the practise courts and in the gym and all this hard work is starting to pay off so I'm really pleased about that."
Jankovic also volunteers to work on behalf of children as the UNICEF Ambassador for Serbia. This week, Jelena Jankovic is competing in the Kremlin Cup in Moscow.