Inferences — Digital SAT Reading & Writing practice
Complete the logic the text supports.
Key ideas to know
Evidence-Based Inference Rule
A passage states: "The city banned single-use plastics last year, and local river pollution levels dropped by forty percent." What can be reasonably inferred? A) Plastics cause all pollution. B) The ban reduced plastic waste in the river. C) Other cities will follow suit. D) Recycling programs failed.
Choice B. An inference must follow very probably from the given facts without adding outside information. The text directly links the ban to lower pollution, making B the only supported conclusion.
Watch out: Choosing an answer that sounds plausible but introduces outside facts or stretches the evidence beyond what the text actually states.
Supported inference
A passage says: “Plants near the vent grew taller than plants farther away, although both groups received the same sunlight and water.” Which inference is best supported? A) Heat or minerals from the vent may help plants grow. B) Sunlight does not matter to any plant. C) The vent will eventually harm the plants. D) Only tall plants are healthy.
A. The text rules out sunlight and water as the difference, so the vent is the likely cause. The other choices go beyond the evidence.
Watch out: Choosing an answer that sounds true in general but adds claims the passage never makes.
Extreme Words in Inferences
A text says: "Many students struggled with the calculus midterm, and several failed to complete the final section." Which inference is flawed? A) The exam was difficult for a portion of the class. B) Every student should retake the course. C) Some test-takers found specific problems challenging. D) Performance varied across the group.
Choice B is flawed because it uses the extreme word "every" and adds an unmentioned idea (retaking the course). The text only mentions struggle and incomplete sections, not universal failure or required retakes.
Watch out: Selecting an answer with absolute terms like always, never, or all when the original text only provides limited or partial evidence.
Clue Words Signal Conclusions
Read: "The archaeologist uncovered ancient pottery shards; _____, the site likely dates back to the Bronze Age." Which word correctly completes the inference? A) however, B) consequently, C) despite, D) whereas.
Choice B. Words like therefore, so, and thus signal that the second clause is a logical conclusion drawn from the first. "Consequently" matches this cause-and-effect reasoning perfectly.
Watch out: Misreading clue words as contrasts or exceptions when they actually point to a logical conclusion or result.
Sample questions
Question 1
Ships crossing the Atlantic in the nineteenth century relied on accurate clocks to determine longitude. A clock that drifted even a few seconds per day could, over a long voyage, produce positional errors of many miles. Ship chronometers were therefore mounted in gimbals, cushioned against vibration, and wound on strict schedules.
Which choice is the most logical inference based on the text?
- Longitude could be determined without any timekeeping device.
- Small timekeeping errors could have serious navigational consequences.
- Nineteenth-century clocks never drifted more than a few seconds per day.
- Gimbals were invented in the nineteenth century.
Show answer and explanation
Answer: Small timekeeping errors could have serious navigational consequences.
The text states that drift of a few seconds daily could yield errors of many miles, which explains the elaborate protective measures — small errors had serious consequences.
Question 2
Urban wildlife often develops traits that differ from rural populations of the same species. City-dwelling birds, for instance, tend to sing at higher pitches, which carry better over low-frequency traffic noise. Researchers studying crested anoles in Puerto Rico found that city lizards have longer limbs and stickier toe pads than forest lizards — traits suited to running on walls and windows rather than branches.
Which choice is the most logical inference based on the text?
- Urban environments can drive physical and behavioral changes in animal populations.
- City animals are healthier than their rural counterparts.
- Traffic noise has no effect on bird populations.
- Anoles are the only lizards that adapt to cities.
Show answer and explanation
Answer: Urban environments can drive physical and behavioral changes in animal populations.
Both examples (birds' pitch, lizards' limbs and pads) show urban conditions shaping traits. The other choices overreach or contradict the text.
Question 3
Medieval scribes frequently left marginal notes in the manuscripts they copied — complaints about cold rooms, dull quills, and long hours. Scholars once dismissed these marginalia as idle doodling, but researchers now catalog them systematically. Because scribes rarely recorded their working conditions elsewhere, such notes are often the only surviving evidence of how manuscript production actually felt to the people performing it.
Which choice is the most logical inference based on the text?
- Medieval scribes were generally dissatisfied with their profession.
- Formal records of scribes' working conditions are scarce.
- Marginalia were intended by scribes as historical documentation.
- Modern scholars no longer study the main texts of manuscripts.
Show answer and explanation
Answer: Formal records of scribes' working conditions are scarce.
The text says scribes 'rarely recorded their working conditions elsewhere,' making marginalia 'the only surviving evidence' — so formal records must be scarce. The other options exceed or distort the text.