A study by a group of dentists has concluded that regular use of a certain brand of mouthwash is as effective as flossing in preventing gum disease. The mouthwash company has released a television ad suggesting that people who do not like flossing can now rely solely on mouthwash and brushing to maintain good dental health. A leading manufacturer of dental floss brought a lawsuit against the mouthwash company demanding that the advertisement be discontinued on the grounds that it is misleading.

Which of the following, if true, provides the strongest support for the dental floss company's claim that the advertisement is misleading?

A) The dental floss manufacturer is concerned that it will lose market share in the dental health market because the advertisement encourages people to switch from dental floss to mouthwash.

B) The dental floss company claims in its own advertisements that brushing and flossing after every meal is the most effective way to maintain good dental health.

C) Although mouthwash is an effective deterrent to gum disease, it is less effective than dental floss at removing plaque and preventing cavities between teeth.

D) Per usage, mouthwash is three times more expensive than dental floss, if the recommended amounts of both products are used.

E) The dentists who conducted the study on the effectiveness of mouthwash in preventing gum disease obtained their funding for the study from a company that manufactures mouthwash.



I was stuck between C and E and finally chose E. OA however is C. I eliminated C on the basis that it says mouthwash is LESS effective than floss; which doesn't necessarily mean that mouthwash is completely in-effective, hence it might still replace floss to maintain "GOOD" dental health.

As an example: If 'A' is excellent and 'B' is 'very good' (in other words B less effective than A), still both A and B will categorize as good and above.

Can someone please advise on this?