X<sub>1</sub>,X<sub>2</sub>是随机变量,其分布函数分别为F<sub>1</sub>(x),F<sub>2</sub>(x),为使F(x)=aF<sub>1</sub>(x)+bF<sub>2</sub>(x)是某一随机变量的分布函数,在下列给定的各组数值中应取()<img src="https://nimg.ppkao.com/2019-04/wangjing/2019041717232186115.jpg?sign=0c6cdea49bdb7d02cebd05b56ef5bb75&t=62d5c450" /><img src="https://nimg.ppkao.com/2019-04/wangjing/2019041717232671079.jpg?sign=3a1a7f65a127316444419a70bd6bacfe&t=62d5c450" />
A、A
B、B
C、C
D、D