Lamp A is less bright than Lamp B; Lamp B is brighter than Lamp C; Lamp C is as bright as Lamp D. Lamp B is brighter than Lam...

Lamp A is less bright than Lamp B; Lamp B is brighter than Lamp C; Lamp C is as bright as Lamp D. Lamp B is brighter than Lamp D and Lamp D is brighter than Lamp A. Which lamp is the brightest?