下列哪一项不是注意力缺陷性多动症的特征()。
A.动作过多
B.行为异常
C.抽动过多
D.情绪异常
E.在意力不集中
参考答案:C
Today _____ people learning English in China is increasing rapidly.[ ]
A. a number of
B. a good many of
C. the number of
D. a great deal of
简述数控电火花线切割加工原理?