Researchers recently discovered that lipstick can become contaminated with bacteria that causes mononucleosis. They found that contamination usually occurs after the lipstick has been used for six months. For that reason, women should
dispose of any lipstick after six months of use.
Which of the following, if true, would most weaken the conclusion above?

Question

Examsnet · Accepted Answer

Correct Answer is :  The researchers found that among women who used lipstick contaminated with bacteria that causes mononucleosis, the incidence of these diseases was no higher than among people who used uncontaminated lipsticks.

GMAT Verbal Reasoning Practice Test 2