A television commercial argued as follows: both the product advertised and its competitor contain the same active ingredients, but the product advertised contains them in higher concentrations; tests show that the higher concentrations are completely safe; since a product that provides faster relief is always preferable, one should use the product advertised.
The television commercial's argument is most vulnerable to criticism on the grounds that itThe commercial says the advertised product has higher concentrations of the same active ingredients and that those concentrations are safe. Then it concludes that the advertised product should be used because faster relief is preferable.
The missing link is that
higher concentration actually means faster relief.
(A) takes for granted that it is true in all cases that products with higher concentrations of active ingredients are more effective than their competitors
This is too broad. The argument does not need to assume this is true in all cases; it only needs it to be true for this product and its competitor.
(B) attempts to establish its conclusion on the basis of evidence that is in principle impossible to disprove
This is not the flaw. The claims about ingredients, concentration, and safety could in principle be tested.
(C) dismisses its competitor's claims because of their source rather than their content
This is irrelevant. The argument does not discuss or dismiss any claim made by the competitor.
(D) attempts to manipulate the emotions of potential customers of the advertised product rather than presenting logically sound reasons for preferring the product advertised
This is not the specific flaw. The argument gives reasons; the problem is that one key logical connection is missing.
(E) takes for granted that the product with the higher concentration of active ingredients provides faster relief than its competitor
This is correct. The commercial moves from higher concentration to the idea that the product provides faster relief, but it gives no evidence that the higher concentration actually produces faster relief.
Answer: (E)