How to answer it
- State each scientist’s explanation in a phrase.
- Ask what result each one predicts.
- Pick the finding that matches one prediction and breaks the other.
Worked example
An original question in the ACT format, already answered.
ACT ScienceWorked example
Scientist 1 says a lake’s algae bloom was caused by fertilizer runoff from nearby farms. Scientist 2 says it was caused by unusually warm water.
Which finding would most weaken Scientist 2’s explanation?
- AThe lake was 4°C warmer than average.
- BA nearby lake with the same warm water but no farm runoff had no bloom.
- CAlgae grow faster in sunlight.
- DThe bloom began in July.
Answer: B. If warm water alone caused blooms, the nearby warm lake should have one too. It didn’t, which weakens Scientist 2. A would support Scientist 2.
The most common trap
Picking evidence that supports the view you were asked to weaken.
Practice it
Hourly Prep’s daily sets mix evaluation of models, inferences, and experimental results with the rest of ACT Science, and send more of it your way when it’s a weak spot. See how the ACT prep plan works, or browse the other ACT skill guides.