包括连续变量和非连续变量样本大小的估计是（）
A.双盲
B.单盲
C.样本含量
D.三盲
E.随机分组
参考答案：C
生石灰二级品要求CaO不小于88%。
Great changes __________ in China in the past few years.
A． were taken place
B． took place
C． have been taken place
D． have taken place
