题目

20世纪中叶以后，移动电话快速发展．移动电话机（                   ）                            A．  既能发射电磁波，也能接收电磁波    B．  只能发射电磁波，不能接收电磁波    C．  不能发射电磁波，只能接收电磁波    D．  既不能发射电磁波，也不能接收电磁波                                                                                                     �My father was reading a newspaper ___ my mother was cooking dinner.A.because B. when C. while D.but