LSAT Explanation PT 43, S3, Q19: Today's farmers plant only a handful

LSAT Question Stem

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

Logical Reasoning Question Type

This is a Weaken 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 argument structure is as follows:

Premise 1: Today's farmers plant only a handful of different strains of a given crop.

Premise 2: Crops lack the diversity that they had only a few generations ago.

Conclusion: A disease that strikes only a few strains of crops would devastate the food supply today, whereas it would have had only minor impact in the past.

To make this more relatable, imagine a group of people who all wear the same type of shoe. If a particular defect is found in that shoe, everyone would be affected. In contrast, if people wore various types of shoes, only those wearing the defective shoe would be impacted. This is similar to the situation with crops; if there is less diversity, a disease affecting a few strains can have a greater impact on the overall food supply.

An "Evaluate" question for this argument could be: "Can the affected crops be replaced quickly enough to prevent a devastating impact on the food supply?"

Now, let's discuss the answer choices for the Weaken question:

a) In the past, crop diseases would often devastate food supplies throughout entire regions.

This answer choice does not weaken the conclusion because it does not provide any information about the current situation or the impact of a disease on today's food supply.

b) Affected crops can quickly be replaced from seed banks that store many strains of those crops.

This is the correct answer choice. If affected crops can be quickly replaced, then the impact on the food supply may not be as devastating as the argument suggests. This weakens the conclusion.

c) Some of the less popular seed strains that were used in the past were more resistant to many diseases than are the strains popular today.

This answer choice actually strengthens the argument by providing evidence that today's strains are less resistant to diseases, making the food supply more vulnerable.

d) Humans today have more variety in their diets than in the past, but still rely heavily on cereal crops like rice and wheat.

This answer choice does not weaken the conclusion because it does not address the impact of a disease on the food supply. It only provides information about the variety in human diets.

e) Today's crops are much less vulnerable to damage from insects or encroachment by weeds than were crops of a few generations ago.

This answer choice does not weaken the conclusion because it does not address the impact of a disease on the food supply. It only provides information about the crops' resistance to insects and weeds.

In conclusion, answer choice (b) is the correct choice as it weakens the argument by suggesting that affected crops can be quickly replaced, potentially preventing a devastating impact on the food supply.