// 1. 统计每个元素出现次数
Sade last toured and released an album 15 years ago
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Optical-based smoke alarms use light instead. They are slightly better at detecting the large smoke particles created by slow, smouldering fires. When such particles enter a chamber in the device, they scatter light from a small light source, which is then picked up by a photoelectric sensor.
Score: 8ProsConsProduces relatively true-to-life photos