LSAT Explanation PT 28, S1, Q5: The number of codfish in the

LSAT Question Stem

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

Logical Reasoning Question Type

This is a Weaken question. 

Correct Answer

The correct answer to this question is D. 

LSAT Question Complete Explanation

First, let's analyze the structure of the argument in the passage. The passage states that the number of codfish in the North Atlantic has declined while the harp seal population has increased. Some people blame the seals for the decline in cod population, but the argument claims that this is unlikely because cod play a negligible role in the seal's diet. The passage presents this as the conclusion. The premise is that cod is not a significant part of the seal's diet.

To better understand this argument, let's use a simple example. Imagine a town where the number of apples has decreased while the number of rabbits has increased. Some people blame the rabbits for the decline in apples, but the argument claims that this is unlikely because apples are not a significant part of the rabbit's diet.

An "Evaluate" question for this argument could be: "Is there any other way in which the increase in the seal population could negatively affect the cod population?"

Now, let's discuss the question type and answer choices. The question type is "Weaken," which means we are looking for an answer choice that, if true, would make the argument's conclusion less likely to be true.

a) This answer choice talks about the inconvenience caused to people who fish for cod due to the presence of seals. However, it doesn't address the relationship between the seal population and the decline in cod population. Therefore, it doesn't weaken the argument.

b) This answer choice suggests that water pollution is a more significant threat to cod than to harp seals. While this provides an alternative explanation for the decline in cod population, it doesn't directly weaken the argument that the increase in seal population is unlikely to have contributed to the decline in cod population. In fact, it might even strengthen the argument by providing another reason for the decline in cod population.

c) This answer choice states that harp seals thrive in water that is too cold for a dense population of cod. Similar to answer choice (b), this might strengthen the argument by showing that seals and cod don't live near each other, making it less likely that the increase in seal population has affected the cod population.

d) This is the correct answer. It states that cod feed almost exclusively on capelin, which is also a staple of the harp seal's diet. This information introduces a new way in which the increase in the seal population could negatively affect the cod population: by competing for the same food source. This weakens the argument that the increase in seal population is unlikely to have contributed to the decline in cod population.

e) This answer choice suggests that the decline in cod population began before the increase in the harp seal population. While this might seem like a good candidate for weakening the argument, it actually further disconnects the two populations by showing that the decline in cod started before the increase in seals. We are looking for an answer that connects the two populations and shows that the increase in seal population could have contributed to the decline in cod population, so this answer choice is not correct.

In conclusion, answer choice (d) is the correct answer because it introduces a new way in which the increase in the seal population could negatively affect the cod population, thereby weakening the argument that the increase in seal population is unlikely to have contributed to the decline in cod population.