Logical reasoning PrepTest 107 · Section 4 · Question 20

This is a tricky answer! It can feel as if it eliminates an alternative cause - other types of radiation. However, remember that the noted cause was the depletion of the ozone layer, not UV-B radiation, so this answer doesn’t eliminate alternatives. If anything, it limits the damage done to amphibians by the ozone depletion to the effects of UV-B. That either doesn’t affect the argument (since it changes nothing), or weakens it by eliminating more ways for the ozone layer depletion to lead to the noted effect, so this is the correct answer.

This is an example of a control - for the species that are less affected by UV-B radiation from the ozone depletion, there’s less of a decline in population. That shows less cause, less effect, strengthening the argument for causality.

This answer establishes that the ozone depletion lines up directly with where the effect is seen, strengthening the argument that it’s the primary cause of it.

This answer eliminates an alternative cause. If their habitat had shrunk, then that may explain the decline in population instead of the ozone depletion. By eliminating that possibility, this answer strengthens the argument.

This can seem out of scope if you didn’t note the timeline in the stimulus (we should have - timelines are always important!). However, the stimulus establishes the past 50 years as the timeline over which the ozone has continuously depleted. If that was matched by a continuous decline in amphibian population, that closely ties the two together, strengthening the argument that there’s a causal relationship between the two.