A lot of ads are aimed speciall _____ teenagers. [ ]
A. at
B. with
C. by
D. in
答案:A
下列文件属于太平天国 ( )
①《天朝田亩制度》②《海国图志》③《资政新篇》④《权利法案》
A.①②
B.③④
C.①③
D.①④
在同一正态总体中抽样有99%的样本均数在下述范围内
A.χ-±2.58SX-
B.χ-±1.96SX-
C.μ±1.96SX-
D.μ±2.58SX-
E.χ-±2.58δX-