SAT Reading and Writing
Inferences
Inferences is a skill in the Information and Ideas domain of the Digital SAT Reading and Writing section. These are practice questions on it, and each answer choice comes with an explanation of why it is right or wrong.
13 questions. After every answer you’ll see why each choice is right or wrong, not just the one you picked.
Sample questions
Open a question to see the answer choices and the correct answer.
Entomologists studying a species of firefly found that males synchronize their light flashes with nearby males during mating displays, flashing in unison rather than at random intervals. When researchers played back recordings of an out-of-sync flash pattern near a group of males, the group took significantly longer to resynchronize than groups exposed to recordings of an already-synchronized pattern. This finding suggests that ______ Which choice most logically completes the text?
- A. synchronized flashing occurs only when researchers are actively observing the fireflies.
- B. an individual firefly's flash timing is influenced by the flash patterns of other fireflies nearby. ✓
- C. female fireflies play no role in selecting a mate based on flash patterns.
- D. fireflies are incapable of producing light unless another firefly is nearby.
Correct answer: B. Since an out-of-sync recording delayed resynchronization, individual fireflies' flash timing must be responsive to the flash patterns of nearby fireflies.
A team studying an ancient trade route found that pottery shards from a distant coastal region appeared in inland settlements only after a mountain pass connecting the two areas was widened around 1200 CE. Before the pass was widened, coastal pottery is nearly absent from inland archaeological sites, despite the coastal region being a known pottery-producing center for centuries prior. This suggests that ______ Which choice most logically completes the text?
- A. inland settlements had no interest in acquiring coastal pottery before 1200 CE.
- B. coastal artisans did not begin producing pottery until after 1200 CE.
- C. the width of the mountain pass, rather than a lack of coastal pottery production, was the primary barrier to trade between the two regions before 1200 CE. ✓
- D. the mountain pass was completely impassable before 1200 CE.
Correct answer: C. Since coastal pottery production predates 1200 CE by centuries but only reaches inland sites afterward, the pass's width, not a lack of production, appears to be the limiting factor.
Researchers comparing two nearby populations of a freshwater snail found that snails in a pond with many fish predators had significantly thicker shells, on average, than snails in a nearby, predator-free pond, even though both ponds had similar water chemistry and food sources. When researchers moved snails from the predator-free pond into cages within the predator-filled pond, exposing them to chemical cues from fish without any actual predation, the caged snails developed thicker shells within weeks. This finding suggests that ______ Which choice most logically completes the text?
- A. fish predators in the pond directly attack and thicken the shells of snails they encounter.
- B. shell thickness in this snail species is determined entirely by genetic differences between the two populations.
- C. the water chemistry of the predator-filled pond directly causes thicker shells, regardless of the presence of predators.
- D. the snails' shell thickness can change in response to environmental cues associated with predators, not only through gradual selection across generations. ✓
Correct answer: D. Since individual snails developed thicker shells within weeks of exposure to predator cues alone, shell thickness must be able to change within an individual's lifetime, not only through selection across generations.
Marine biologists tracking sea otters off the California coast noticed that otters in kelp forests with sea star populations intact had significantly lower urchin densities nearby than otters in kelp forests where sea stars had been wiped out by disease. Sea urchins are a shared prey item for both otters and sea stars, and unchecked urchin populations are known to graze kelp forests down to bare rock. Which choice most logically completes the text: The pattern suggests that ______
- A. sea stars and otters may work as complementary predators, and losing one predator can leave urchin populations, and the kelp forest itself, more vulnerable. ✓
- B. otters are less effective hunters than sea stars in every kelp forest ecosystem studied.
- C. sea urchin populations are unrelated to the health of kelp forests.
- D. sea star disease has no measurable effect on kelp forest ecosystems.
Correct answer: A. Correct — the data comparing forests with and without sea stars, combined with the shared urchin prey and urchins' known effect on kelp, supports the idea that both predators together help control urchins more effectively than either alone.
A team studying online consumer behavior found that shoppers shown a product with a countdown timer indicating limited-time availability added it to their cart 40 percent more often than shoppers shown the identical product without a timer. However, return rates for items purchased under a timer were also more than double the return rates for items purchased without one. Which choice most logically completes the text: This finding suggests that ______
- A. countdown timers have no meaningful effect on consumer purchasing decisions.
- B. urgency cues like countdown timers may prompt purchases shoppers would not otherwise make on reflection, some of which they later reconsider. ✓
- C. shoppers who see countdown timers make more thoughtful purchasing decisions than those who do not.
- D. return rates are unrelated to how a product is marketed to consumers.
Correct answer: B. Correct — the combination of a higher cart-add rate and a much higher return rate together suggest that the timer prompts hastier purchases that shoppers are more likely to later regret and return.