室分分布系统产生导频污染的原因不包含下列哪些()
A.网络参数设置不当
B.合路器故障
C.信号源选取不当
D.信号分配不当
参考答案:B
After school we went to the reading-room to do some reading, only to be told that it ____________.
A.was decorated
B.had decorated
C.had been decorating
D.was being decorated
多动症的最主要临床表现是()
A.明显的注意力不集中,持续时间短暂
B.活动过度
C.学习困难
D.常伴品行障碍
E.冲动