[题目]设随机变量x,y相互独立且均服从正态-|||-分布N(μ,σ^2),若概率 (aX-bYlt mu )=dfrac (1)(2) ,则 ()-|||-A. =dfrac (1)(2) ,=dfrac (1)(2)-|||-B. =dfrac (1)(2) ,=-dfrac (1)(2)-|||-C. =-dfrac (1)(2) ,=dfrac (1)(2)-|||-D. =-dfrac (1)(2) ,=-dfrac (1)(2)