以下哪项不是注意缺陷多动障碍（ADHD）的临床表现（）
A.情绪不稳
B.活动过度
C.智力落后
D.注意力集中困难
E.学习困难
参考答案：C
坐板凳是指在网上论坛中第一个回帖。
We _____ each other since you left. [ ]
A. didn't see
B. hadn't
C. haven't seen
D. have seen
