Critical Reasoning

Over the last century, paleontologists have used small differences between fossil specimens to classify triceratops into sixteen species. This classification is unjustified, however, since the specimens used to distinguish eleven of the species come from animals that lived in the same area at the same time.

Which of the following, if true, would enable the conclusion of the argument to be properly drawn?

(A) Not every species that lived in a given area is preserved as a fossil.
(B) At least one individual of every true species of triceratops has been discovered as a fossil specimen.
(C) No geographical area ever supports more than three similar species at the same time.
(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.

I am confused about 2 things related to this question.

1.) What kind of a question is this must be true, strengthen or assumption.?

2.) Based on what type it is,how to attack such a question?

E[/spoiler]

1)Assumption Question
2) Close the Gap
Is the OA C ? E actually is the Opposite

Great question. I don't think that I have seen a stem like this but it is an assumption question. Must be true questions generally don't have a conclusion, and strengthen questions ask for evidence to support the conclusion. This stem asks for information that must exist (ie an additional premise) for the conclusion to be drawn.

The argument

p: paleontologists have used small differences between fossil specimens to classify triceratops into sixteen species.
p: the specimens used to distinguish eleven of the species come from animals that lived in the same area at the same time.
c: This classification (into 16 species) is unjustified

(A) This does nothing to the justification of the classification into 16 species. It may indicate that there are more than 16 species but that has no effect on the conclusion

(B) This does the opposite of (A), showing that all species of triceratops are represented in the fossil samples. Again this does nothing to the conclusion for the same reason as (A)

(C) This is correct. It shows that the argument is strong by showing that a single area cannot have more than 3 species (of triceratops) when the paleontologists claim to have found 11 in the same place.

(D) This would actually weaken the conclusion since it provides evidence that the fossils display "marked variation", thus showing that the classifications are correct.

(E) This would actually weaken the argument as it shows that fossil samples are at least as distinctive as fossils from different areas. This shows that the area that the fossils are found doesn't matter to classification which is the premise that the argument is based on (ie this attacks premise 2)

Awesome post Idoolit. Got the concept now.