来自同一总体中的两个样本中，以下哪种指标值小的其样本均数估计总体均数更可靠？（）
A.Sx
B.S
C.x
D.CV
E.S2
参考答案：A
—What makes her so frightened?
—Oh,it is the mouse that she______on her bed while looking for her watch.
A．came about
B．came across
C．came through
D．came up
抗爆性较好的（）是汽油的理想的组分。
A.高度分支的异构烷烃
B.正构烷烃
C.环烷烃
D.分支少的异构烯烃
