Premise: paleontologists have used small differences between fossil specimens to classify triceratops into sixteen species

Counter premise: however, since the specimens used to distinguish eleven of the species come from animals that lived in the same area at the same time

Conclusion: the classification is unjustified.

Now we have to find a link between the counter premise and the conclusion. This link will allow the conclusion to be properly drawn


(A) Not every species that lived in a given area is preserved as a fossil.

This means that some species that lived in a given area are preserved as a fossil. This supports the paleontologists view

(B) At least one individual of every true species of triceratops has been discovered as a fossil specimen.

same as A

(C) No geographical area ever supports more than three similar species at the same time.

This restricts to three the number of species in a geographical area at the same time. Let's put both premises together to see if we can draw the conclusion

since the specimens used to distinguish eleven of the species come from animals that lived in the same area at the same time and since no geographical area ever supports more than three similar species at the same time, we can conclude that it is impossible to classify triceratops into sixteen species.

This sounds correct

(D) In many species, individuals display quite marked variation.


(E) Differences between fossil specimens of triceratops that came from the same area are no less distinctive than differences between specimens that came from different areas.

This means that we should not distinguish between triceratops that came from the same are and triceratops that came from different areas. This supports the paleontologists view that we can use the differences in fossils to classify triceratops.