LSAT Explanation PT 41, S1, Q2: A study of plaque buildup on

LSAT Question Stem

Which one of the following, if true, most helps to explain the relative amounts of plaque buildup found in the three groups? 

Logical Reasoning Question Type

This is a Paradox question. 

Correct Answer

The correct answer to this question is B. 

LSAT Question Complete Explanation

First, let's understand the passage: A study was conducted on three groups of people to analyze plaque buildup on their teeth. Group 1 used the same toothbrush for a year, Group 2 used the same toothbrush but sterilized it monthly, and Group 3 used a new toothbrush every month. At the end of the year, Group 1 and Group 2 had the same amount of plaque buildup, while Group 3 had less plaque buildup.

The question type is a Paradox, and we need to resolve the paradox by finding an explanation for the different amounts of plaque buildup in the three groups.

Now, let's analyze each answer choice:

a) This choice talks about bacteria growth on toothbrushes that remain unsterilized for more than a month. However, it doesn't explain why Group 2, which sterilized their toothbrushes, still had the same plaque buildup as Group 1. This choice doesn't resolve the paradox.

b) This choice suggests that new toothbrushes have stiffer bristles, which are more effective in inhibiting plaque buildup. Over time, the mechanical action of brushing destroys the stiffness of the bristles. This explains why Group 3, which used new toothbrushes every month, had less plaque buildup compared to the other groups. This choice resolves the paradox and is the correct answer.

c) This choice mentions a new method of measuring plaque buildup, but it doesn't provide any distinction between the groups or explain the difference in plaque buildup. It doesn't resolve the paradox, so it's incorrect.

d) This choice talks about the previous brushing habits of people in Group 3. However, the study focused on plaque buildup during the study period, so this information doesn't explain the difference in plaque buildup between the groups. This choice doesn't resolve the paradox and is incorrect.

e) This choice states that people in Group 2 and Group 3 brushed their teeth as vigorously as those in Group 1. While it might support the validity of the study, it doesn't explain the difference in plaque buildup between the groups. This choice doesn't resolve the paradox and is incorrect.

In conclusion, the correct answer choice is (B), as it provides a clear explanation for the difference in plaque buildup between the three groups. The stiffness of the bristles on new toothbrushes inhibits plaque buildup more effectively than the bristles on old toothbrushes, even if they are sterilized.