For a command-of-evidence question involving competing explanations, break the claim into its required parts and evaluate each option against all of them. Prefer controlled evidence that isolates the proposed cause and connects it to the stated mechanism; evidence that merely supports one part of the claim or leaves a major alternative explanation unresolved is weaker.
Hints
- Hint 1
Separate the explanations
Ask whether each finding favors protection from predators, greater access to food, or another feature of the modules.
- Hint 2
Check the controls
The strongest finding should eliminate prey availability and construction material as alternative explanations.
- Hint 3
Connect structure to behavior
Look for evidence that the gobies respond differently to crevices under conditions associated with danger.
Step-by-step
- Step 1
Identify the competing explanations
The researchers must distinguish between two possible reasons for the gobies’ greater abundance: increased access to prey and protection from predators.
- Step 2
Look for controlled evidence of the proposed mechanism
The strongest evidence should hold prey availability constant, isolate the presence of crevices, and connect the gobies’ response to a sign of predation risk.
- Step 3
Select the most complete support
The laboratory finding does all three. The structures have the same material, prey numbers are equal, and the preference for crevices appears only after predator odor is introduced. This directly links the crevices to the gobies’ perception of danger.