LSAT Explanation PT 43, S3, Q23: Each of many different human hormones

LSAT Question Stem

Which one of the following most accurately expresses the main conclusion of the argument above? 

Logical Reasoning Question Type

This is a Main Conclusion question. 

Correct Answer

The correct answer to this question is B. 

LSAT Question Complete Explanation

First, let's analyze the argument in the passage. The passage presents the following structure:

1. Each of many different human hormones can by itself raise the concentration of glucose in the blood. (Observed Phenomenon)

2. The reason for this is probably a metabolic quirk of the brain. (Main Conclusion)

3. Although most human cells can produce energy from fats and proteins, brain cells can use only glucose. (Premise)

4. If blood glucose levels fall too low, brain cells will rapidly starve, leading to unconsciousness and death. (Intermediate Conclusion)

The main conclusion of the argument is that the reason many different hormones can each independently raise blood glucose levels is probably a metabolic quirk of the brain. The passage provides evidence to support this conclusion by explaining that brain cells can only use glucose for energy, and if glucose levels fall too low, brain cells will starve, leading to unconsciousness and death.

Now let's discuss the question type and what it's asking us to do. The question type is Main Conclusion, which means we need to identify the statement that most accurately expresses the main conclusion of the argument.

Let's go through each answer choice:

a) Each of many different human hormones can by itself raise blood glucose levels.

- This answer choice simply restates the observed phenomenon mentioned in the passage. It does not represent the main conclusion, which is an explanation for this phenomenon.

b) The reason that many different hormones can each independently raise blood glucose levels is probably a metabolic quirk of the brain.

- This answer choice accurately expresses the main conclusion of the argument. It provides an explanation for the observed phenomenon mentioned in the passage.

c) Although most human cells can produce energy from fats and proteins, brain cells can produce energy only from glucose.

- This answer choice is a premise supporting the main conclusion. It does not represent the main conclusion itself.

d) If blood glucose levels fall too low, then brain cells starve, resulting in loss of consciousness and death.

- This answer choice is an intermediate conclusion that further supports the main conclusion. It does not represent the main conclusion itself.

e) The reason brain cells starve if deprived of glucose is that they can produce energy only from glucose.

- This answer choice is not stated in the passage, and the main conclusion must always be a statement that is explicitly mentioned in the passage.

Based on our analysis, the correct answer is B, as it most accurately expresses the main conclusion of the argument.