两大样本均数比较，推断μ1=μ2是否成立，可用（）
A.χ2检验
B.u检验
C.方差分析
D.以上三种均可以
E.t检验
参考答案：D
If Newton lived today, he would be surprise by what () in science and technology.
A. had discovered
B. had been discovered
C. has discovered
D. has been discovered
肇庆古称端州，至哪个朝代始称肇庆？（）
A、汉代
B、唐代
C、北宋
