Okay so let's first break down the argument in the passage:
We are told that the school principal believes that student failures are caused by bad teaching. Then we are told that in a small amount of time after, failing grades disappeared from the school. The principal took this as evidence that the teaching had improved at the school.
What is wrong with this argument? Well, we have absolutely no evidence to back up the principal's belief. At this point, the principal arbitrarily believes that bad teaching has caused the student failures. The moment the student failures disappear, for no reason at all, the principal believes this proves that the teaching is no longer bad, i.e. the teaching has improved.
This argument is similar to me saying: I believe that Greg's fatigue is caused by a bad diet. A little bit later, Greg's fatigue disappears. I take this as evidence that Greg has begun to eat better. But, I have not been given any actual evidence or information about Greg's diet changing. It could be that Greg is merely getting more sleep or that Greg is taking sleeping pills.
Now, let's take a look at answer choice (E):
We are told that the nutritionist believes that the weight gain of the team members was caused by their thinking of food too often. Then we are told that the team members reported that they had stopped thinking of food so often and the nutritionist took this as evidence that the weight gain had stopped.
Well, remember, our argument follows the reasoning that one believe X is caused by Y and they take the presence of not X to prove that Y no longer exists.
Answer choice (E) not only has some semblance of viable evidence: the team has actually reported that they had stopped thinking of food so often, whereas in the argument we do not actually know whether teaching has improved, but the reasoning in answer choice (E) follows a completely different pattern.
The reasoning in (E) shows that one (the nutritionist) believes that X (the team's weight gain) is caused by Y (their thinking of food too often), and once it has been reported that Y no longer exists (the team reports that they had stopped thinking of food so often), they conclude that X no longer exists (the weight gain has stopped).
As you can see, answer choice (E) does not follow the same flawed pattern of reasoning as the passage.
Hope that clears things up! Please let us know if you have any other questions.
