A.1080
B.1200
C.1240
D.1560
[单选题]A.1080B.1200C.1240D.1560
[单选题]A.1080B.1200C.1240D.1560
[单选题]A.1080B.1200C.1240D.1560
[单选题]A.1080B.1200C.1240D.1560
[单选题]A.1080B.1200C.1240D.1560
[单选题]A.420B.450C.500D.540
[单选题]A.420B.450C.500D.540
[B单选题]分布1、分布2、分布3的标准差分别为()。A.B.C.D.