The observed effect we are trying to explain is the acne outbreak.
People believe that it is being caused by eating large amounts of chocolate, given the temporal sequence of eating large amounts of chocolate being invariably followed by an acne breakout.
However, we know that inferring a causal relationship solely based on a temporal sequence is flawed logic.
The author has an alternative theory for this observed effect, i.e. stress.
The author cites several recent scientific studies that show hormonal changes associated with stress can cause acne and there is good evidence that people fond of chocolate tend to eat more chocolate when they are under stress.
Notice that the author is providing additional evidence that points to an alternative explanation.
The problem with (C) is not that scientific studies cannot be considered scientific authorities.
Rather, the issue with (C) is that the author is not dismissing people's opinion solely based on the superior authority of science.
Also, note that it is not actually being dismissed out of hand as the author states, "it is LIKELY that common wisdom has mistaken an effect for a cause."
The author does not state it is certain.
Hope this helps! Please let us know if you have any other questions.
