How much are the checkers? [ ]
A. It's Friday.
B. Twenty-eight yuan.
C. We fly kites.
答案:B
若一组数据a1,a2…an的方差为2,则新数据3a,3a2,3a3…3an的方差为[ ]
A.18
B.6
C.12
D.2
疱疹性咽峡炎的病原体为()。
A.流感病毒
B.副流感病毒
C.柯萨奇病毒
D.单纯疱疹病毒
E.腺病毒