LSAT 152 | Section 4 | Logical Reasoning: Q12

LR Question 12 Explanation

QUESTION TEXT: The Amazon River flows eastward into the Atlantic Ocean …

QUESTION TYPE: Strengthen

CONCLUSION: The Amazon River once flowed into the Pacific Ocean.

REASONING: Some Amazon freshwater fish descended from saltwater fish that lived in the Pacific but not the Atlantic.

ANALYSIS: The hypothesis is that the river used to connect to the Pacific. To strengthen that, we want something that makes this explanation more likely.

Timing is usually a pretty good way to figure things out. The Andes Mountains are now blocking access to the Pacific. But what if the fish existed before the Andes formed? Maybe then there used to be a connection.

___________

1. This weakens the ancestry link.
2. CORRECT. If those Pacific fish existed before the Andes formed, that supports the idea that there used to be a connection between the Amazon and the Pacific.
3. This just says Atlantic and Pacific fish can be related, but doesn’t really help explain this specific case.
4. We already know it’s cut off by the Andes, so explaining how cut off it is doesn’t really help.
5. This makes transitions harder (few fish survive both environments), which could weaken the argument.