In the oceanic ecosystem of the Azure Trench, any species of deep-sea squid that survived … — LSAT

In the oceanic ecosystem of the Azure Trench, any species of deep-sea squid that survived the sudden temperature drop of the Late Holocene possessed a rare genetic mutation conferring thermal resilience. Yet, marine biologists note that prior to the temperature drop, the vast majority of deep-sea squid species in the Azure Trench did not possess this mutation. Furthermore, while many species lacking the mutation migrated to shallower waters during the temperature drop, no species possessing the mutation migrated out of the Azure Trench. Every migrating species encountered intense predation from surface predators, and only those migrating species capable of rapid camouflage avoided extinction.

Which of the following statements is most strongly supported by the information above?

A
Most of the deep-sea squid species that migrated to shallower waters possessed the capability for rapid camouflage.
B
Any deep-sea squid species in the Azure Trench that possessed the thermal resilience mutation survived the sudden temperature drop.
C
No deep-sea squid species lacking the rare genetic mutation survived the sudden temperature drop.
D
The sudden temperature drop of the Late Holocene caused the deep-sea squid species in the Azure Trench to develop the rare genetic mutation.
Most of the deep-sea squid species present in the Azure Trench prior to the temperature drop did not survive the temperature drop within the Azure Trench.Answer

Answer

Most of the deep-sea squid species present in the Azure Trench prior to the temperature drop did not survive the temperature drop within the Azure Trench.

The stimulus provides a strict conditional relationship: Survival in the Azure Trench requires possessing the rare genetic mutation. This means that lacking the mutation guarantees a species did not survive in the trench (the contrapositive). The stimulus also provides a demographic fact: the vast majority of species present prior to the event did not possess this mutation. Combining these two premises logically proves that the vast majority of the original species did not survive within the Azure Trench.

Step-by-Step Solution

Analyze the conditional requirement for survival within the trench.

If a species survived the temperature drop in the Azure Trench, then it possessed the rare genetic mutation (Survive in Trench -> Mutation).

The stimulus explicitly states that 'any species... that survived... possessed a rare genetic mutation'.

Formulate the contrapositive of the survival condition.

If a species did not possess the rare genetic mutation, it did not survive the temperature drop within the Azure Trench (No Mutation -> Did NOT Survive in Trench).

Contrapositive reasoning is a fundamental valid inference tool for translating conditional statements.

Evaluate the quantitative demographic information provided.

Prior to the drop, the 'vast majority' (more than half) of the deep-sea squid species in the Azure Trench did not possess the mutation.

This establishes the logical quantity (most/majority) connected to the necessary condition.

Synthesize the demographic quantity with the conditional contrapositive.

Since most original species lacked the mutation, and lacking the mutation guarantees non-survival within the trench, it must be true that most of the original species did not survive within the trench.

Combining a 'most' premise with a definitive absolute rule (All A are B, Most C are A, therefore Most C are B) yields a strongly supported inference.

Key Concept

Combining Quantifiers with Conditional Contrapositives

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