A certain species of coral that flourishes on a reef off the North Carolina coast provides shelter for more than...

GMAT Critical Reasoning : (CR) Questions

Source: Mock

Critical Reasoning

Logically Completes

MEDIUM

...

Notes

Post a Query

A certain species of coral that flourishes on a reef off the North Carolina coast provides shelter for more than 300 species. Among these species is a crab that feeds on the reef's abundant seaweed. These crabs are able to survive on the reef only because the coral provides crannies in which they can hide to escape their many predators. The provision of benefits, however, extends in both directions, since ______________.

Which of the following most logically completes the passage?

crabs of this species are rarely found among coral that grows in waters deeper than those of the reef off North Carolina

crabs of this species cannot survive in a well-lit area if no corals grow there

no other species that find shelter among corals off the North Carolina coast compete with crabs of this species for food

the unfettered growth of seaweed severely inhibits the growth of corals

this species of coral secretes a substance that is nutritious to crabs and other crustacians

Solution

Passage Analysis:

Text from Passage	Analysis
A certain species of coral that flourishes on a reef off the North Carolina coast provides shelter for more than 300 species.	What it says: Coral on North Carolina reef gives shelter to 300+ species What it does: Sets up the ecosystem scenario and shows coral's role as protector What it is: Author's factual claim Visualization: Coral = Big apartment building housing 300+ different animal tenants
Among these species is a crab that feeds on the reef's abundant seaweed.	What it says: One of those 300+ species is a crab that eats seaweed from the reef What it does: Zooms in on one specific example from the broad group mentioned before What it is: Author's supporting detail
These crabs are able to survive on the reef only because the coral provides crannies in which they can hide to escape their many predators.	What it says: Crabs need coral's hiding spots to survive - without them, predators would get the crabs What it does: Explains why the coral is essential for the crab's survival What it is: Author's causal explanation Visualization: Coral crannies = Safe hiding spots, Crabs without hiding spots = Dead crabs
The provision of benefits, however, extends in both directions, since ______.	What it says: Benefits flow both ways (coral helps crab AND crab helps coral) What it does: Signals that we're missing the other half of this mutual relationship What it is: Author's transitional claim with blank to fill

Argument Flow:

The passage starts by establishing a ecosystem where coral shelters many species, then focuses on crabs as a specific example. It explains how coral benefits crabs by providing hiding spots from predators. Finally, it signals that this is a two-way relationship, setting up the blank for how crabs benefit the coral in return.

Main Conclusion:

There is no main conclusion yet - this is an incomplete argument that needs the blank filled to show how crabs benefit the coral.

Logical Structure:

This is a reciprocal relationship structure: Coral helps crab (established) + Crab helps coral (missing piece) = Mutual benefit relationship. We need to find what the crab does for the coral to complete this balanced exchange.

Prethinking:

Question type:

Logically Completes - We need to find what information would best complete the argument's logical flow

Precision of Claims

The passage establishes a one-way benefit (coral helps crab survive) and signals there's a two-way relationship, so we need the specific way the crab benefits the coral

Strategy

Since the passage says 'benefits extend in both directions,' we need to identify how the crab helps the coral in return. The crab eats seaweed, so we should think about how this seaweed-eating behavior could benefit the coral. The completion should create a logical mutualistic relationship.

Answer Choices Explained

crabs of this species are rarely found among coral that grows in waters deeper than those of the reef off North Carolina

This choice tells us about where crabs are rarely found (deeper waters), but this doesn't explain how crabs benefit the coral in return. We need information about what crabs do FOR the coral, not where they typically live. This doesn't complete the 'benefits extend in both directions' logic.

crabs of this species cannot survive in a well-lit area if no corals grow there

This choice reinforces that crabs need coral for survival in well-lit areas, but this is just restating the coral-helps-crab direction we already know. We need the opposite direction - how crabs help coral. This doesn't fulfill the 'both directions' requirement.

no other species that find shelter among corals off the North Carolina coast compete with crabs of this species for food

This choice discusses competition between species for food, but competition isn't a benefit. Even if true, this doesn't show how crabs benefit the coral - it just says other species don't compete with crabs. We need a positive action crabs take that helps coral.

the unfettered growth of seaweed severely inhibits the growth of corals

This choice creates the perfect reciprocal relationship. If unchecked seaweed growth 'severely inhibits the growth of corals,' and we know crabs 'feed on the reef's abundant seaweed,' then crabs benefit coral by eating the seaweed that would otherwise harm coral growth. This completes the mutual benefit: coral provides shelter → crabs survive → crabs eat seaweed → coral can grow better.

this species of coral secretes a substance that is nutritious to crabs and other crustacians

This choice suggests coral secretes nutritious substances for crabs, but this is another example of coral helping crabs, not crabs helping coral. We already know coral benefits crabs through shelter - adding nutrition is still the same direction. We need how crabs benefit coral.

Rate this Solution

Tell us what you think about this solution

...

Forum Discussions

Start a new discussion

Post

Previous Attempts

Loading attempts...