Question 56·Medium·Inferences
City researchers monitored rat activity with motion-activated cameras near trash bins for eight weeks. In week 3, the sanitation department shifted trash collection on half the blocks from late evening to early morning; the other blocks kept their usual schedule. From week 3 onward, camera counts of rats declined steadily on the blocks with the new morning pickups but stayed roughly the same on the others. Sanitation logs show that the total amount of trash collected per block did not change during the trial. Based on this information, it can most reasonably be inferred that ______
Which choice most logically completes the text?
For Reading & Writing inference questions, first restate in your own words what happens and what changes in the passage, then ask: "What conclusion is most strongly supported only by this information?" Eliminate any answers that (1) contradict a stated fact, (2) go beyond the scope of the data (like making citywide claims from a local study), or (3) introduce new causes or explanations that are not implied. Often, the correct choice will make a modest, specific claim that directly matches the experimental pattern described, rather than a broad or dramatic conclusion.
Hints
Locate the comparison in the passage
Focus on what happens after week 3 to the rat counts on the blocks that changed pickup times versus those that did not.
Identify the one key difference
Ask yourself: after week 3, what is the only intentional difference between the two sets of blocks? How does that relate to the different rat activity patterns?
Use the sanitation logs
The passage tells you whether the amount of trash per block changed. Eliminate any choice that conflicts with that detail.
Watch for overgeneralizations
Be careful about answer choices that make claims about the whole city or about what is sufficient to solve the problem. Check whether the passage actually provides evidence that broad.
Step-by-step Explanation
Understand the experiment setup
The city watched rat activity near trash bins for eight weeks using cameras. In week 3, only half the blocks changed their trash pickup from late evening to early morning; the other blocks stayed on the usual schedule. This means the only planned difference between the two groups after week 3 was the pickup time.
Focus on the key results and controls
From week 3 onward, rat counts from the cameras went down steadily on the blocks with the new morning pickups, but stayed about the same on the blocks that kept the evening schedule. The sanitation logs say the total amount of trash per block did not change during the trial, so we know the quantity of trash stayed constant; only the timing of pickup changed for some blocks.
Decide what can be most reasonably inferred
Because (1) only the pickup time changed for half the blocks, (2) only those blocks showed a steady decline in rat activity, and (3) the amount of trash stayed the same, the most reasonable conclusion is that changing trash collection to the morning probably reduced rat activity on the affected blocks. This matches choice A.