Question 117·Hard·Inferences
Since 2014, a citizen‑science project has asked volunteers to report how many stars they can see from their neighborhoods. Over the past decade, participants in hundreds of cities have reported a steady decline in the number of visible stars, suggesting increasing skyglow. Yet satellite measurements of nighttime radiance over many of the same regions show a slight decrease. During this period, numerous municipalities replaced orange‑emitting high‑pressure sodium streetlights with energy‑efficient LEDs that emit more blue‑rich light, and the satellites used are comparatively insensitive to blue wavelengths. Taken together, these observations most strongly suggest that ______
Which choice most logically completes the text?
For “complete the text” inference questions, first summarize in your own words what the passage is showing—often a pattern, contrast, or problem—and then pay special attention to the final sentence before the blank, which usually contains the key clue for the logical conclusion. Ask, “What overall idea would tie these details together or explain this contradiction?” Then test each option against the passage: eliminate choices that introduce new ideas not mentioned, contradict the given information, or use extreme language like “any,” “never,” or “exclusively.” Choose the option that directly uses the passage’s details to resolve the situation or state the most reasonable conclusion, without going beyond what the text supports.
Hints
Locate the conflict
Notice that citizen reports suggest more skyglow, while satellite measurements show a slight decrease in nighttime radiance. Think about why two measurement methods might disagree.
Focus on the last sentence
Look closely at the information about cities switching to blue‑rich LEDs and the satellites being insensitive to blue wavelengths. Ask yourself how that detail could explain the disagreement between ground observations and satellite data.
Check what the completion must do
The best answer should (1) explain why citizens report fewer visible stars while (2) satellites show a slight decrease in radiance, and (3) make clear use of the information about blue‑rich LEDs and satellite sensitivity—without introducing extreme or unrelated claims.
Step-by-step Explanation
Understand what the question is asking
You are asked: “Taken together, these observations most strongly suggest that ______” and to pick the sentence that most logically completes the text.
So your task is to:
- Combine all the given facts.
- Decide what overall conclusion or explanation they most strongly suggest (not just something that might be true).
Summarize the key facts
Identify the important pieces of information:
- Citizen reports: Since 2014, volunteers report fewer visible stars, which suggests increasing skyglow (brighter night skies that hide stars).
- Satellite data: Over the same regions, satellites show a slight decrease in nighttime radiance (they see things as getting a bit darker, not brighter).
- Lighting change: Many cities replaced orange sodium lights with blue‑rich LEDs.
- Satellite limitation: The satellites used are comparatively insensitive to blue wavelengths (they don’t “see” blue light very well).
These points set up a contradiction (citizens see more skyglow, satellites see less) and then describe a detail (blue‑rich LEDs + satellite insensitivity) that can explain the contradiction.
Identify what the combined facts suggest
Ask yourself: How could the switch to blue‑rich LEDs and the satellites’ poor blue sensitivity explain why people see more skyglow but satellites record less radiance?
- If lights are now emitting more blue light, but satellites can’t detect blue well, then:
- Ground observers would see brighter skies and fewer stars (more skyglow).
- Satellites might miss much of that new blue light, so their measurements could incorrectly suggest that brightness has not increased—or has even decreased slightly.
So, the most logical conclusion is that the satellite readings are underestimating the real increase in skyglow because of their lack of blue sensitivity.
Match this inference to the answer choices
Now compare this idea to the choices:
- You want the choice that explains the mismatch by saying that the change to blue‑rich LEDs made the blue‑insensitive satellites fail to detect the full increase in brightness.
Choice B states exactly that: the shift to blue‑rich LEDs likely caused satellites that lack blue sensitivity to miss increases in skyglow. This directly uses the information about blue‑rich LEDs and satellite insensitivity to resolve the conflict between citizen reports and satellite data, so B is the correct answer.