An inference question about a study tests what you can conclude from the reported results. Start with the sentence introducing the blank, then name what each sample showed and when. When several records are combined, ask what they support together and which possible causes they help test. Predict the smallest supported conclusion, remembering that the best explanation isn't a proven cause. Wrong choices often add a possible story without evidence that it actually happened.
Hints
- Hint 1
The blank asks for a conclusion that uses all the records. Compare the pollen changes in both lakebeds, including when they began.
- Hint 2
Look for records that test other possible causes. What do the charcoal particles and climate records tell you about the interval with changed pollen?
- Hint 3
Read the description of the grass pollen closely. Use that detail to connect its increase with the oak decline.
Step-by-step
Connect the pollen pattern and test its cause
Step 1Link the pollen changes
Cho found that the proportion of agricultural grass pollen in both samples doubled while old-growth oak pollen sharply declined. What must the conclusion explain? Since the blank asks us to use the records together, we need one cause that fits both pollen changes around 2,800 years ago, not a story about oak loss alone.
- Step 2
Check fire and climate
Could fire or climate account for the shift? Charcoal is a common proxy for wildfire, meaning an indirect sign of fires, and it didn't increase during the interval. The climate records also show no significant shifts in temperature or precipitation. These checks give us no evidence of increased wildfire or a major climate shift to explain the pollen changes.
- Step 3
Use the specific grass clue
What does agricultural grass pollen add beyond a general increase in grasses? It links the rise to farming, while the falling oak pollen points to less old-growth forest. Together, those clues suggest forest was being replaced by farmland, which would explain both pollen changes. This is a best-supported explanation, not proof of exactly how the trees disappeared or a claim that every other possible cause has been tested.
- Step 4
Choose the right strength of claim
How strong can the claim be? The records support a best explanation, not absolute proof. The choice about human expansion of agriculture uses most plausibly, so it draws a careful conclusion from the farming clue and the checks on fire and climate. Choice D.