题目

如果X是离散型随机变量，EX=6,DX=0.5,X1=2X-5，那么EX1和DX1分别是(    )A.EX1=12,DX1=1                          B.EX1=7,DX1=1C.EX1=12,DX1=2                          D.EX1=7,DX1=2 答案：思路解析：因为E(aX+b)=aEX+b,D(aX+b)=a2DX，由已知可得EX1=7,DX1=2，应选D.答案：D﹣Which song do you like better，Lucy？﹣I prefer the song Little Apple can attract many people．（ ）A．which B．whoC．whom D．where