Which one of the following characteristics is not common between birds and mammals?

The correct option is D Viviparity
Birds and Mammals share a lot of similarities which include Ossified Endoskeleton, Homeothermic, use of lungs for breathing. But mammals are Viviparous, have mammary glands to feed their young, and hair covering their body. While birds lay eggs with nutrition in it for their incubation period and have modified scales called feathers.

So, the correct option is 'Viviparity'.