Strengthen the argument.A. Most of the twelve species of lizards native to the Randall valley were already declining in population thirty years ago.
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Incorrect. If anything, it weakens the argument instead of strengthening it. All the lizards might have disappeared even without the climate change.
B. The very same species of lizards can still be found in a neighboring valley, where the destruction of the forests was not accompanied by a rise in temperature.
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Correct. The valley from the question stem has 2 factors -- no trees and climate change -- and no lizards. The neighboring valley has only 1 factor -- no trees -- and tons of lizards. Therefore, climate change has been responsible to a large degree for the disappearance of lizards in the first valley.
C. Scientists believe that even if the region can be replanted it will take many generations before the lizards can be reintroduced into the forests.
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Out of scope. The hypothesis is about the disappearance of lizards, not about what would bring them back.
D. Two of the twelve species of lizard have been on the worldwide endangered species list for fifty years.
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Out of scope, too narrow. A correct answer would say something important about all 12 species, not about only some of them.
E. The loss of the forests also caused a reduction in the population of snails, slugs and worms, the three main sources of food for the lizards.
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Weakens the hypothesis instead of strengthening it. E basically says that lizards have died out because of absence of trees, not because of the climate change.