This question is asking you to determine which "principle" helps justify the reasoning. As with any logical reasoning question, the first step is to break down the argument into its component parts:
Premise: Computer modeling of reasoning tasks is easier than for processing sense images. Premise: Computers can defeat chess champions but can't see. Conclusion: It appears we understand our minds better than our senses.
Now see if you can determine what principle is behind the argument. To me, it appears that the backbone of the argument is that since we can model X and not Y, we understand X better.
Answer Choices: (A) is incorrect. The argument is not about the "degree of difficulty" of certain tasks but rather is about our understanding of ourselves.
(B) is incorrect. The argument is not about understanding a computer's ability to perform a task, but about our ability to make a computer do something.
(C) is incorrect. The argument never discusses the concept of "true intelligence."
(D) is correct. This answer choice maps on to the principle we found above. It says that the easier it is to model something, the better we understand it. This is very similar to what we found above: since we can model X and not Y (aka it's easier to model X then Y), we understand X better.
(E) is incorrect. The conclusion does not talk about the usefulness of modeling.