In grasslands near the Namib Desert there are "fairy circles"—large, circular patches that are entirely devoid of veg...

shunhe on May 13, 2020

Hi @hatemz,

Thanks for the question! So let’s take a look at the stimulus. We’re told that fairy circles and sand termites often go together, and scientists think that sand termites cause these circles to form (since the circles are entirely devoid of vegetation).

Now we’re asked to strengthen the scientists’ hypothesis. Let’s take a look at (E), which tells us that species of animals that feed sand termites are often found living near fairy circles. But this is pretty irrelevant; it doesn’t tell us anything about the relation between burrowing and fairy circles. At best, it tells us that there are probably sand termites in fairy circles. But the stimulus already flat-out tells us that there are sand termites found at every investigated fairy circle. So (E) doesn’t actually add any new information in that regard, and doesn’t strengthen.

(A), on the other hand, does strengthen the argument, because if the plants are damaged only at the roots, that would eliminate some alternate explanations for why there are no plants, and help support the idea that burrowing (which would damage the roots) could be the reason for the damage.

Hope this helps! Feel free to ask any other questions that you might have.