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14 Oct 2023, 01:00
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Difficulty:
35%
(medium)
Question Stats:
76% (01:46) correct
24%
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wrong
based on 168
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A study of plague buildup on teeth used three randomly assigned groups of people who brushed their teeth twice a day for a year. People in Group 1 used the same toothbrush all year. People in Group 2 used the same toothbrush all year but sterilized it each month. People in Group 3 used a new, sterile toothbrush each month. At the end of the year, people in Group 1 and 2 had the same amount of plague buildup as each other, while people in Group 3 had less plague buildup.
Which one of the following, if true, most helps to explain the relative amounts of plague buildup found in the three groups?
(A) The Buildup of plague on teeth, which brushing twice a day helps to prevent, is accelerated by the growth of bacteria on toothbrushes that remained unsterilized for more than a month.
(B) The stiffness of the bristles on new toothbrushes, which the mechanical action of brushing destroys after several months, inhibits the buildup of plague.
(C) The people who did the study measured the amount of plague buildup by a new method not usually employed by dentists.
(D) Before they joined the study, some of the people in Group 3 had been in the habit of brushing their teeth only once a day.
(E) The people in Group 2 and Group 3 brushed their teeth as vigorously as did the people in Group 1.
Which one of the following, if true, most helps to explain the relative amounts of plague buildup found in the three groups?
(A) The Buildup of plague on teeth, which brushing twice a day helps to prevent, is accelerated by the growth of bacteria on toothbrushes that remained unsterilized for more than a month.
(B) The stiffness of the bristles on new toothbrushes, which the mechanical action of brushing destroys after several months, inhibits the buildup of plague.
(C) The people who did the study measured the amount of plague buildup by a new method not usually employed by dentists.
(D) Before they joined the study, some of the people in Group 3 had been in the habit of brushing their teeth only once a day.
(E) The people in Group 2 and Group 3 brushed their teeth as vigorously as did the people in Group 1.
14 Oct 2023, 11:01
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Harshani
Let's evaluate each option:
(A) This suggests that bacteria growth on toothbrushes which are unsterilized for more than a month accelerates plaque buildup. However, both Group 1 (used the same toothbrush all year) and Group 2 (sterilized it each month) had the same amount of plaque buildup. This statement doesn't differentiate between Group 1 and 2, so it doesn't help explain why Group 3 had less plaque.
(B) This suggests that new toothbrushes have stiff bristles which prevent plaque buildup, and the bristles lose this effectiveness after a few months. This explains why Group 3 (who used a new brush every month) had less plaque than the other two groups, whose brushes would have softened over time.
(C) The method used to measure plaque doesn't provide an explanation for the difference in plaque buildup among the groups.
(D) This fact about Group 3's previous brushing habits doesn't explain the results. If anything, it might suggest Group 3 should have more plaque buildup if they used to brush less often before the study. It doesn't support the observed difference.
(E) This simply states that all groups brushed with the same vigor, so it doesn't explain why Group 3 had less plaque buildup than Groups 1 and 2.
19 Oct 2023, 09:52
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A study of plague buildup on teeth used three randomly assigned groups of people who brushed their teeth twice a day for a year. People in Group 1 used the same toothbrush all year. People in Group 2 used the same toothbrush all year but sterilized it each month. People in Group 3 used a new, sterile toothbrush each month. At the end of the year, people in Group 1 and 2 had the same amount of plague buildup as each other, while people in Group 3 had less plague buildup.
Which one of the following, if true, most helps to explain the relative amounts of plague buildup found in the three groups?
(A) The Buildup of plague on teeth, which brushing twice a day helps to prevent, is accelerated by the growth of bacteria on toothbrushes that remained unsterilized for more than a month. - WRONG. More than a month is out of the scope of the passage.
(B) The stiffness of the bristles on new toothbrushes, which the mechanical action of brushing destroys after several months, inhibits the buildup of plague. - CORRECT. Destruction over a 12 month period is more leading to more buildup of bacteria as compared to destruction over a month.
(C) The people who did the study measured the amount of plague buildup by a new method not usually employed by dentists. - WRONG. Irrelevant.
(D) Before they joined the study, some of the people in Group 3 had been in the habit of brushing their teeth only once a day. - WRONG. Whatever happened before is useless.
(E) The people in Group 2 and Group 3 brushed their teeth as vigorously as did the people in Group 1. - WRONG. Not a helpful comparison for what we are looking for.
Only A and B are contenders. A being a trap leaves us with B.
Answer B.
Which one of the following, if true, most helps to explain the relative amounts of plague buildup found in the three groups?
(A) The Buildup of plague on teeth, which brushing twice a day helps to prevent, is accelerated by the growth of bacteria on toothbrushes that remained unsterilized for more than a month. - WRONG. More than a month is out of the scope of the passage.
(B) The stiffness of the bristles on new toothbrushes, which the mechanical action of brushing destroys after several months, inhibits the buildup of plague. - CORRECT. Destruction over a 12 month period is more leading to more buildup of bacteria as compared to destruction over a month.
(C) The people who did the study measured the amount of plague buildup by a new method not usually employed by dentists. - WRONG. Irrelevant.
(D) Before they joined the study, some of the people in Group 3 had been in the habit of brushing their teeth only once a day. - WRONG. Whatever happened before is useless.
(E) The people in Group 2 and Group 3 brushed their teeth as vigorously as did the people in Group 1. - WRONG. Not a helpful comparison for what we are looking for.
Only A and B are contenders. A being a trap leaves us with B.
Answer B.
