We are looking for an answer that will describe a flaw in the argument.
The argument proceeds by noting that there is a clear connection between smoking and lung disease and cancer, but we should not make tobacco companies liable. They support this with an analogy to candy companies, who are similarly responsible for tooth decay.
A claims the argument fails to establish the scientific documentation behind the fact that candy causes tooth decay. The author offers us pretty strong wording, stating that this connection is "undeniable." This is not that different from calling the connection a well established fact, as the author calls the connection between smoking and cancer. Regardless, even if the connection is slightly weaker, candy is being used as an analogy, and the connection would not need to be airtight.
E gives us reason to doubt that the analogy is valid. The author thinks that companies should not be liable in the case of one bad thing because they are not liable for another bad thing, but E suggests that these two bad things are in fact completely different in nature. If the harms are not comparable, then the analogy falls apart.