D-spaces

We use U-sticky sets to show that box products of scattered spaces of height 1 are D-spaces and to simplify the proof of van Douwen and Lutzer that a subspace of a linearly ordered space is a D-space iff no closed subset is stationary. Analogously, we show that a subspace of a product of finitely many ordinals is a D-space iff it is metacompact iff no closed subset is stationary. We examine the proof that metric spaces are D-spaces and obtain a new characterization of semistratifiability.