题目

阅读下面短文，从短文后各题所给的A、B、C和D四个选项中，选出可以填入空白处的最佳选项。 It’s about 250 miles from the hills of west-central lowa to Ehlers’ home in Minnesota. During the long trip home, following a weekend of hunting. Ehlers   41   about the small dog he had seen   42   alongside the road. He had   43   to coax（哄）the dog to him but, frightened, it had   44  . Back home, Ehlers was troubled by that   45   dog. So, four days later, he called his friend Greg, and the two drove   46  . After a long and ca 电磁波在发射过程中必须有调制器，调制器在发射过程中的作用是 [　　] A．将高频信号加到低频振荡电流上去 B．将低频信号加到低频振荡电流上去 C．将高频信号加到高频振荡电流上去 D．将低频信号加到高频振荡电流上去