配对资料均数比较的I检验的自由度为
A．2nB．2n-1C．2n-2D．n-1E．以上都不对
参考答案：D
Bob never drives _____ his brother. [ ]
A. so careful as
B. so carefully as
C. carefully as
D. so careful
在168÷21=8中，______是______的倍数，______是______的因数．
