Some paleontologists believe that certain species of dinosaurs guarded their young in protective nests long after the young hatched. As evidence, they cite the discovery of fossilized hadrosaur babies and adolescents in carefully designed nests. But similar nests for hatchlings and adolescents are constructed by modern crocodiles, even though crocodiles guard their young only for a very brief time after they hatch. Hence, __. Which one of the following most logically completes the argument? ['paleontologists who believe that hadrosaurs guarded their young long after the young hatched have no evidence to support this belief', 'we will never be able to know the extent to which hadrosaurs guarded their young', "the construction of nests for hatchlings and adolescents is not strong evidence for the paleontologists' belief", 'it is unclear whether what we learn about hadrosaurs from their fossilized remains tells us anything about other dinosaurs']