Drivers are alerted when they become drowsy by audio and visual alarms 一旦司机昏昏欲睡，声音和图像警示器将对他们提出警告。
2.
Helen : that ' s good idea . don ' t forget to ask about fire prevention too . smoke alarms and sprinklers aren ' t always enough 海伦：好主意。别忘了还要问消防措施，烟雾警示器与喷淋装置并不是对每种状况都能应付得了。
