LSAT Explanation PT 28, S1, Q20: If the economy is weak, then

LSAT Question Stem

If the statements above are true, then which one of the following must be false? 

Logical Reasoning Question Type

This is a Must Be False question. 

Correct Answer

The correct answer to this question is A. 

LSAT Question Complete Explanation

This LSAT problem is a Must Be False (MBF) question type, which means we are looking for the answer choice that must be false given the information provided in the passage. Let's first analyze the passage and then discuss each answer choice in detail.

Passage analysis:

1. If the economy is weak, then prices remain constant, and unemployment rises.

2. Unemployment rises only if investment decreases.

3. Investment is not decreasing.

From the passage, we can infer that unemployment is not rising, and as a result, the economy is not weak. Now let's evaluate each answer choice.

a) Either the economy is weak or investment is decreasing.

This answer choice must be false because both claims in the either/or statement are not true. We know from the passage that the economy is NOT weak, and investment is NOT decreasing.

b) If unemployment rises, then prices remain constant.

This answer choice could be true. We don't know for sure whether these two phenomena are conditionally related based on the information given in the passage.

c) The economy is weak only if investment decreases.

This answer choice must be true. Although investment decreasing is not the only necessary condition for the economy to be weak, it is one of several necessary conditions based on the stimulus.

d) Either the economy is weak or prices are remaining constant.

This answer choice could be true. We know that the economy is NOT weak, but it is possible that prices are remaining constant. To conclude otherwise would be to make a Mistaken Negation.

e) Either unemployment is rising or the economy is not weak.

This answer choice must be true because we know from the passage that the economy is not weak. Since the economy is not weak, at least one part of the either/or statement is true.

In summary, the correct answer is A because it is the only answer choice that must be false given the information provided in the passage.