"BG-ALERT：紧急警报" "BG-ALERT：警告" "BG-ALERT：信息" "BG-ALERT：人员失踪警报" "BG-ALERT：测试警报" "极端和严重威胁" "生命财产遭受极端和严重威胁" "信息" "信息类消息" "人员失踪警报" "人员失踪消息" "测试警报" "接收测试消息"