实验性研究所具有的特点有（）。
A.可操纵性
B.样本量大
C.设立对照组
D.单纯抽样
E.随机分组
参考答案：A, C, E
The author was required to submit an_______of about 200 words together with his research paper．
A．edition
B．editorial
C．article
D．abstract
铭旌
