9.当x→0时, (x)=a(x)^3+bx 与 (x)=(int )_(0)^sin x((e)^(t^2)-1)dt 是等价无穷小,则 ()-|||-(A) =dfrac (1)(3) =1 (B) =3, b=0 (C) =dfrac (1)(3) =0 (D) =1, b=0 A