参考答案

正确答案：helicopter service
helicopter service 解析：由题干关键词the newest form. of transportation和towns定位到最后一段的第三句。Smaller planes connect nearby cities and towns，and often the towns themselves are connected to their air- ports by helicopter service。小型飞机连接了附近的城市和城镇，而这些城镇到小型机场之间常有直升机服务。