"999"在英语中表示为"nine nine nine"。
这个号码的来源是英国的紧急呼叫电话号码，即"emergency call number"。在英国，人们可以拨打999来报警、求救或请求医疗急救。
例句1: "If there's an emergency, always call 999." (如果有紧急情况，一定要拨打999。)
例句2: "I dialed 999 but the pne was busy." (我拨了999，但是电话占线了。)
例句3:"The operator on the other end of the pne instructed me to call 999 for an ambulance." (电话另一端的接线员告诉我拨打999请救护车。)