LSAT Explanation PT 34, S3, Q3: Sigatoka disease drastically reduces the yield

LSAT Question Stem

Which one of the following is an assumption on which the argument depends? 

Logical Reasoning Question Type

This is a Necessary Assumption question. 

Correct Answer

The correct answer to this question is B. 

LSAT Question Complete Explanation

Let's first analyze the argument in the passage and identify its structure. The argument discusses Sigatoka disease, a fungus that affects banana trees and reduces their yield. The author mentions that fungicides can control the disease but can be harmful to humans living nearby. Therefore, fungicides are not suitable for small banana groves in populated areas. However, the author concludes that most of the world's banana crop is not seriously threatened by Sigatoka disease because large banana plantations are isolated and can safely use fungicides.

Here's the structure of the argument:

1. Premise: Sigatoka disease reduces banana yield.

2. Premise: Fungicides can control the disease but are harmful to humans.

3. Premise: Fungicides are unsuitable for small groves in populated areas.

4. Premise: Most large plantations are isolated and can safely use fungicides.

5. Conclusion: Most of the world's banana crop is not seriously threatened by Sigatoka disease.

Now, let's create an "Evaluate" question for this argument: "Do large plantations produce most or all of the world's bananas?"

The question type for this problem is Necessary Assumption, which means we need to identify the assumption on which the argument depends.

Now let's go through each answer choice:

a) It will eventually be possible to breed strains of bananas that are resistant to Sigatoka disease.

- This answer choice is not necessary for the argument. The argument's conclusion is about the current threat of Sigatoka disease, not potential future solutions.

b) Large plantations produce most or all of the world's bananas.

- This answer choice is the correct one. The argument assumes that large plantations, where fungicides can be safely used, are responsible for most or all of the world's banana production. If this were not the case, the conclusion that most of the world's banana crop is not seriously threatened by Sigatoka disease would not hold.

c) Sigatoka disease spreads more slowly on large plantations than in small banana groves.

- This answer choice is not necessary for the argument. The argument focuses on the use of fungicides to control the disease, not on the rate at which it spreads.

d) Sigatoka disease is the only disease that threatens bananas on a worldwide scale.

- This answer choice is not necessary for the argument. The argument is specifically about Sigatoka disease and its impact on the banana crop, not about other potential diseases.

e) Most of the banana trees that have not been exposed to the Sigatoka fungus grow in small banana groves.

- This answer choice is not necessary for the argument. The argument is about the threat of Sigatoka disease and the use of fungicides to control it, not about where unexposed banana trees grow.

In conclusion, the correct answer is B, as it is the necessary assumption on which the argument depends. Large plantations must produce most or all of the world's bananas for the conclusion that most of the world's banana crop is not seriously threatened by Sigatoka disease to be valid.