# List all recoverable files
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.
，更多细节参见WPS官方版本下载
for (int i = 0; i < n - 1; i++) {，这一点在Line官方版本下载中也有详细论述
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