Explanation
Choice A is the best answer. If the same standard is used to evaluate both easy and difficult tasks, then it would appear that some foxes are better at solving problems than other foxes, when in fact such disparities are simply due to differences in the difficulty of the tasks.
Choice B: This choice is irrelevant because the researchers did not evaluate whether or not the foxes could complete a task.
Choice C: The text makes it clear that the results are not reliable and suggests that it cannot be applied even to Vulpes vulpes.
Choice D: The text does not comment on the implications of the artificial problems and the problems found in nature.
✨ Expert's Tip ✨
Identify the statement in the text about the flaw in the experiment. Then, choose the answer choice that most accurately reflects the possible consequence of that flaw.