(2012?洛阳模拟)如图,在直角梯形ABCD中,AD⊥AB,AB∥DC,AD=DC=1,AB=2,动点P在以点C为圆心,且与直线BD相切的圆上或圆内移动,设AP=λAD+μAB(λ,μ∈R),则λ+μ取值范围是( )A.[1,2]B.[2,4]C.[2,+∞)D.(-∞,1]