LSAT Explanation PT 43, S3, Q8: Studies suggest that, for the vast

LSAT Question Stem

Which one of the following, if true, would most seriously weaken the argument? 

Logical Reasoning Question Type

This is a Weaken question. 

Correct Answer

The correct answer to this question is C. 

LSAT Question Complete Explanation

The question type for this problem is Weaken, which means we need to find an answer choice that undermines the conclusion or the relationship between the premises and the conclusion.

Let's first analyze the argument in the passage. The argument can be broken down into two premises and one conclusion:

Premise 1: For the vast majority of people who have normal blood pressure, any amount of sodium greater than that required by the body is simply excreted and does not significantly raise blood pressure.

Premise 2: Only persons who have high blood pressure and whose bodies are incapable of safely processing excess sodium need to restrict their sodium intake.

Conclusion: People with normal blood pressure who can process excess sodium do not need to restrict their sodium intake.

To help understand this argument, let's use a simple example. Imagine a group of people at a party. Some people can eat a lot of salty snacks without any problems, while others have a hard time digesting the salt and may feel unwell. The argument is saying that only the people who have trouble digesting the salt need to be careful about how many salty snacks they eat.

An "Evaluate" question for this argument could be: "Can consuming excess sodium over time have any negative effects on people with normal blood pressure?"

Now let's examine each answer choice:

a) High blood pressure is more harmful than was previously believed.

- This answer choice would motivate people with high blood pressure to address their condition, but it doesn't provide a reason for people with normal blood pressure to restrict their sodium intake. Therefore, it doesn't weaken the conclusion.

b) High blood pressure is sometimes exacerbated by intake of more sodium than the body requires.

- This answer choice only shows that excess sodium intake can worsen an existing high blood pressure condition, but it doesn't provide a reason for people with normal blood pressure to restrict their sodium intake. Thus, the conclusion remains unaffected.

c) Excess sodium intake over time often destroys the body's ability to process excess sodium.

- This is the correct answer choice. If it's true that consuming excess sodium over time can impair the body's ability to process excess sodium, then even people with normal blood pressure need to restrict their sodium intake. This weakens the author's claim that only certain groups of people need to restrict their sodium intake.

d) Every human being has a physiological need for at least some sodium.

- The conclusion argues that certain groups of people need to restrict their sodium intake, not eliminate it altogether. Stating that everyone needs some sodium does not weaken the conclusion.

e) Any sodium not used by the body will increase blood pressure unless it is excreted.

- Since people with normal blood pressure do excrete any amount of sodium not used by the body, this answer does not weaken the author's conclusion.