支气管哮喘中起主要作用的Ig是（）
A.IgG
B.IgM
C.SIgA
D.IgE
E.IgD
参考答案：D
The use of the F - distributed test statistic,,to compare the variances of two populations requires all of the following EXCEPT:（）
A. two samples are of the same size.
B. samples are independent of one another.
C. populations are normally distributed.
调节分油器供油量，可以解决（）
A.各润滑点供油不均
B.润滑油不能供到润滑点
C.经常转动油杯盖
D.管路堵塞现象
,to compare the variances of two populations requires all of the following EXCEPT:（）