注意力缺陷多动症首选的治疗药物为A．苯巴比妥 B．左旋多巴 C．哌醋甲酯(利他林)

28. My English teacher has given me so much help that I really want to do something for him ______.

A．in return

B．in fact

C．in surprise

D．in turn

盒子里装7个白球，3个红球，2个黑球，摸到白球的可能性最大．______．

I found _____ very difficult to learn maths well.　 [ ]

A. what

B. it

C. that

D. this

莫维斯线

BIRCH是一种（）。

A.分类器

B.聚类算法

C.关联分析算法

D.特征选择算法