A. If duckbills whipped their tails faster than monitor lizards do, the duckbill's tail would have been effective at warding off the duckbills' fiercest predators.- Effectiveness not mentioned in the passage
B. Duckbills used their tails to strike predators, and their tailbones were frequently damaged from the impact.- No damage mentioned in passage
C. Using their tails was not the only means duckbills had for warding off predators.- Only means not mentioned
D. Duckbills were at much greater risk of being killed by a predator than monitor lizards are.- comparison of risk not mentioned
E. The tails of duckbills, if used to ward off predators, would have been more likely than the tails of monitor lizards to sustain damage from the impact.- correct