虽然美国的灯塔在外观和结构上存在一些差异，但它们确有些共同之处，比如都有灯标、有住房、有时还有钟(后来改用雾角)。
Notwithstanding differences in appearance and construction, most American lighthouses Shared several features: a light, living quarters and sometimes a bell (or later, a foghorn).
雾在十点钟时消散了。
用0.8M的柠檬酸汽雾剂喷15分钟诱导猪咳嗽，由一个熟练的观察者统计30分钟的咳嗽次数。
Coughing was induced by challenging pigs with an aerosol of 0.8 m citric acid over 15 min. Coughs were counted by a trained observer for 30 min.
用0.8M的柠檬酸汽雾剂喷15分钟诱导猪咳嗽，由一个熟练的观察者统计30分钟的咳嗽次数。
Coughing was induced by challenging pigs with an aerosol of 0.8 m citric acid over 15 min. Coughs were counted by a trained observer for 30 min.
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