θ∈(-π/2，π/3)，——》π/6+θ∈(-π/3，π/2)，sin(π/6+θ)=√3/3>0，——》π/6+θ∈(0，π/2)，——》cos(π/6+θ)=√[1-sin^2(π/6+θ)]=√6/3，——》cos(11π/6-θ)=cos(-π/6-θ)=cos(π/6+θ)=√6/3，答案选D。——》
