瓶颈的用法和样例：
例句
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啤酒瓶底的沉淀物一到瓶颈部位，就不要往外倒啤酒了。此时你的一杯啤酒会金灿灿地发亮，酒泡鼓出酒杯口，而又不会溢出杯外。
As soon as the sediment starts creeping up the shoulder of the bottle, stop pouring. You should now have a glass of star-bright beer with a head(of foam) that stands proud of the glass but does not overflow.
