下棋“落棋不悔”,足球“越位犯规”,车辆通行遵守“红灯停、绿灯行”等这些都是我们应该遵循的[ ]
A、规则
B、程序
C、纪律
D、习惯
答案:A
On hearing the news, he stood up, and. ________the dictionary lying open on the desk, out of the classroom.
A.leaving; rushed
B.left; rushed
C.leaving; rushing
D.left; rushing
画出扬声器系统简单分频器线路图。