以下各类媒体之中属于传输媒体的是（）。 ["磁盘","喇叭","光缆","话筒"]
何谓低频调幅电路？
在以下叙述中不正确的是： 建立用户自定义的过程（） ["是为了提高程序的效率","是为了提高程序的可读性","是为了提高程序员的生产效率","过程的递归调用能提高程序的执行效率"]
何谓高频调幅电路？
Among the basic categories of equipment, which of the following are used to convert the hydraulic energy into linear motion?（） ["Hydraulic pumps","Valves","Hydraulic cylinders","Hydraulic motor"]
简述车轮虫病的病源。
