是什么原因导致这条奇怪的无形分界线跨越法国西南部，穿过意大利、接近佛罗伦萨，又继续向东穿过黑海中部？

What could be the cause of this strange invisible dividing line that skims across south-west France, cuts through Italy close to Florence, and continues eastwards through the middle of the Black Sea?

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第三站是泰国的凯其纳布利，两国的分界线在桂河中穿过。

A third call is made at Katchanaburi in Thailand, where the line crosses the River Kwai.

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分界线从小镇中央穿过。

The dividing line ran through the center of town.

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