Match each argument on the left with the evidentiary finding on the right that most effectively strengthens its central conclusion.
- Marine biologists observed that deep-sea vent crabs graze on bacterial mats almost exclusively immediately following pulses of dissolved methane from hydrothermal vents. They concluded that methane surges directly trigger the crabs' grazing activity.In controlled laboratory aquariums where water temperature, lighting, and bacterial density were held constant, introducing dissolved methane pulses reliably initiated grazing behavior in deep-sea vent crabs.
- A developmental study found that children whose parents frequently used spatial terms during block play scored significantly higher on geometric rotation tests three months later than peers. The researchers concluded that hearing spatial terms actively enhances geometric reasoning in young children.Children evaluated as having identical baseline spatial aptitude before the study demonstrated geometric rotation score gains that correlated directly with the frequency of parental spatial language.
- To curb urban vehicular emissions, a metropolitan transit agency eliminated fares on its light-rail network. Because total rail ridership increased by 40 percent over the subsequent six months, planners concluded that the fare-free policy successfully lowered automotive carbon emissions.A substantial proportion of the newly gained light-rail passengers shifted their daily commute from driving personal gasoline-powered automobiles rather than from walking or cycling.
Answer
The marine biology argument pairs with the finding isolating methane in a controlled aquarium; the spatial language argument pairs with the finding controlling for children's baseline spatial aptitude; and the transit policy argument pairs with the finding confirming that new light-rail riders shifted specifically from gasoline automobiles.
Each matched pair directly targets and resolves the core analytical vulnerability of its argument. For the marine biology argument, the controlled aquarium finding eliminates environmental confounding variables. For the developmental study, controlling for baseline aptitude rules out selection bias and reverse causation. For the transit policy, demonstrating that new riders displaced automobile trips confirms that increased ridership actually reduced automobile emissions.
Step-by-Step Solution
Key Concept
Strengthening causal and inductive arguments by isolating causal variables, controlling for baseline selection bias, and confirming essential substitution mechanisms.