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Question

Difficulty: HardStrengthening Arguments

Environmental scientists recently deployed underwater acoustic speakers broadcasting healthy reef soundscapes along a degraded coastline to attract free-swimming fish larvae, hoping to regenerate local kelp forests. Within six months of continuous broadcast, fish larval settlement along the treated coastline tripled, and local kelp canopy density increased by 40 percent. The scientists concluded that the soundscape-induced influx of fish larvae directly accelerated the recovery of the kelp forest. Which of the following, if true, most strengthens the scientists' argument?

  1. The predominant species of fish larvae attracted by the soundscapes feed aggressively on juvenile sea urchins, which are the primary herbivores responsible for destroying kelp holdfasts in the region.Answer
  2. B
    The artificial low-frequency soundscapes also attract adult herbivorous fish that feed extensively on young kelp fronds before the plants reach maturity.
  3. C
    Coastal tourism operators in the vicinity recorded a substantial increase in diving bookings following the announcement of the reef soundscape initiative.
  4. D
    Unusually cool ocean water temperatures, which are known to promote rapid kelp proliferation, prevailed throughout the entire six-month trial period.
  5. E
    The audio tracks used for the acoustic broadcasts were recorded at pristine coral reefs located thousands of miles away from the test coastline.

Answer

The argument is most strengthened by the statement establishing that the attracted fish larvae consume juvenile sea urchins, the primary destroyers of kelp holdfasts.
The conclusion claims that the influx of fish larvae directly caused the kelp forest's recovery. The statement about fish larvae preying on juvenile sea urchins supplies a direct biological mechanism connecting fish larvae to kelp survival: by consuming sea urchins (which destroy kelp holdfasts), the larvae reduce kelp mortality, directly explaining how their presence accelerates kelp canopy growth.

Step-by-Step Solution

1
Analyze the core argument structure.
Premise 1: Soundscapes increased fish larvae settlement threefold. Premise 2: Kelp canopy density increased by 40%. Conclusion: The influx of fish larvae directly accelerated the kelp forest recovery.
Identifying the leap from correlation (larvae increase coincided with kelp increase) to causation (larvae caused kelp increase) is necessary to determine what support is required.
2
Identify the logical gap or missing link.
The argument assumes a causal connection between the presence of fish larvae and the growth of kelp without explicitly stating how fish larvae benefit kelp.
To strengthen a causal argument, an option must provide a plausible biological mechanism connecting the cause to the effect or rule out alternative causes.
3
Evaluate the choices against the logical gap.
The option stating that the larvae feed on sea urchins (which destroy kelp) supplies the exact causal mechanism needed to show that fish larvae actively protect kelp.
Connecting fish larvae behavior directly to the suppression of kelp predators validates the author's causal conclusion.

Key Concept

Strengthening Causal Arguments by Supplying a Causal Mechanism
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Topics

Strengthening Arguments

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