Correct answer is B.A. This option suggests that contamination occurs regardless of how well the mascara is sealed. However, it
does not weaken the suggestion that mascara brushes become contaminated after 6 months or that they should not be used beyond that period.
B. This option indicates that brushes used for longer than 6 months do not necessarily have more bacteria than those used for 6 months. This finding
would weaken the suggestion, as it implies that the 6-month cutoff may not be relevant to contamination levels.
C. This option addresses the researchers' understanding of the contamination process but does not directly affect the validity of the 6-month recommendation. Knowing the cause of contamination is not essential to the conclusion.
D. This option raises a concern about other contaminants but does not address the specific issue of bacterial contamination or the 6-month guideline.
E. This option suggests that contamination may not lead to eye infections or conjunctivitis, which would weaken the reason for limiting mascara use to 6 months. However, it does not directly challenge the 6-month guideline based on bacterial levels.