First, I have to say that the OA for the first question is A, not E.
As for question 2, you must answer the question in relation to the information provided in the last sentence. When you see these questions that relate to specific parts of the passage, you must go to those parts and read them carefully. This question becomes difficult because the last sentence has a pretty crazy structure with a leading clause followed by some modifying text with two parenthetical statements. You have to focus on the key points: keystone status depends on the context - geography, diversity, and length of interaction.
2. Which of the following, if true, would most clearly support the argument about keystone status advanced in the last sentence of the passage?
A. A species of bat is primarily responsible for keeping insect populations within an ecosystem low, and the size of the insect population in turn affects bird species within that ecosystem. No discussion of context here.
B. A species of iguana occupies a keystone role on certain tropical islands, but does not play that role on adjacent tropical islands that are inhabited by a greater number of animal species. This shows how the geographical context (different tropical islands with different species diversities) impacts keystone status. This fits perfectly with the argument in the last sentence.
C. Close observation of a savannah ecosystem reveals that more species occupy keystone roles within that ecosystem than biologists had previously believed.While this discusses keystone roles, it doesn't talk about differences in context impacting keystone status.
D. As a keystone species of bee becomes more abundant it has a larger effect on the ecosystem it inhabits. No discussion of how context impacts keystone status.
E. A species of moth that occupies a keystone role in a prairie habitat develops coloration patterns that camouflage it from potential predators. Again, no discussion of context impacts on keystone status.
Kyle Widdison | Manhattan GMAT Instructor | Utah
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