Inferences

American Diploma › Digital SAT Reading and Writing — Complete Course

What this question type tests

In an Inferences question, the passage builds an argument or explains a set of facts, and then stops. The last sentence ends with a blank: ______. The question (in our words) is always close to: "Which choice most logically completes the text?" The four choices are possible endings. You must choose the one that follows logically from what the passage has already said — no more and no less.

Inferences is part of the Information and Ideas domain, together with Central Ideas and Details, Command of Evidence — Textual, and Command of Evidence — Quantitative. These four skills together make up about 26% of the scored Reading and Writing questions (12–14 questions across both modules). Each question has one short passage of 25–150 words — often science or social science, sometimes history or the humanities — and four choices.

Many students find these the hardest Reading questions, because the passage often describes a study or a debate in dense, academic language. But the logic is usually simple. Do not confuse this with a vocabulary blank: in a Words in Context question the blank is a word; in an Inferences question the blank is the conclusion of an argument, usually a whole clause.

The method: find the gap in the argument

1. Read the whole passage once for the story. Who thought what? What was discovered? Most passages follow one of these shapes: "Old belief → new evidence → so…", "Rule → case → so…", or "Fact A + fact B → so…".
2. Look hard at the sentence with the blank. Its first words tell you the job: "Therefore / Thus / This suggests that" = a conclusion; "However" or "but" = a contrast; "If… then" = a condition.
3. Find the gap. Ask: "What has the passage set up but not yet said?" Which two facts have not yet been connected? That connection is the answer.
4. Predict an answer in your own words before you read the choices. Keep it modest: "So maybe X is not the only reason."
5. Match and eliminate. Choose the choice closest to your prediction. Cross out choices that contradict the passage, go beyond it (too strong), bring in outside information, or reverse the logic.
6. Final check: read the passage + your choice as one paragraph. Does every step follow? Could the author have written exactly this?

Three kinds of logic you must know

1. Old view → new evidence. The passage describes what scientists or historians used to think, then reports a new finding that does not fit. The blank almost always says the old view may be wrong or incomplete. Words to notice: "long assumed", "traditionally", "However, a recent study…".

2. Conditional logic (if / only if / unless). These need care, because the test checks whether you confuse a necessary condition with a sufficient one.

3. Contrast logic. When the passage says "Although X…", "However…", "Yet…", "Unlike…", the conclusion turns AGAINST what came before the contrast word. Ask: "What does the surprising fact change?" If most cold-climate animals are large, but one is small and survives anyway, the conclusion is that it must survive by another method — not that size never matters.

Worked examples

Worked example 1 — Old view → new evidence

Because the dinosaur Kelvosaurus had unusually long hind legs, paleontologists long assumed that it was a fast runner. A recent study, however, examined a set of its fossilized footprints. The prints were short and closely spaced, and they were left in firm mud that would not have slowed the animal down. Therefore, ______

Question: Which choice most logically completes the text?

• A) long legs do not help any animal to run fast.
• B) Kelvosaurus may have moved more slowly than paleontologists had previously believed.
• C) Kelvosaurus could not run at all and spent most of its life standing still.
• D) the mud must have been much softer than the researchers thought.

Answer: B

• A — ✗ Wrong. Too broad. The study is about one dinosaur; it says nothing about every animal.
• B — ✓ Correct. This connects the new evidence (short, close steps in firm mud) to the old belief (fast runner) and correctly concludes the old belief may be wrong. Note the careful word "may".
• C — ✗ Wrong. Too strong. One set of slow footprints shows it was walking slowly at that time; it does not prove it could never run.
• D — ✗ Wrong. Contradicts the passage, which says the mud was firm.

Note: the detail "firm mud that would not have slowed the animal down" closes a possible escape route (the animal might have been slowed by the ground). Details like this are there to make one conclusion the only logical one.

Worked example 2 — Conditional logic

The flame lily, a flowering plant grown in greenhouses, will produce flowers only if it receives at least 12 hours of uninterrupted darkness for several nights in a row. In one greenhouse, gardeners kept a group of flame lilies under lamps for 16 hours every day, and none of the plants flowered. Gardeners who want flame lilies to flower in time for a winter festival should therefore ______

Question: Which choice most logically completes the text?

• A) make sure that the plants receive at least 12 hours of uninterrupted darkness each night for several nights before the festival.
• B) increase the number of hours that the plants spend under the lamps each day.
• C) place the plants in darkness for 12 hours on a single night, which will guarantee that they flower.
• D) stop growing the plants in greenhouses, since greenhouse plants never flower.

Answer: A

• A — ✓ Correct. Darkness is a necessary condition ("only if"), and 16 hours of light leaves only 8 hours of darkness. So gardeners must meet the condition: 12+ hours of uninterrupted darkness for several nights.
• B — ✗ Wrong. Reversed. More light means even less darkness.
• C — ✗ Wrong. Two errors: one night is not "several nights", and a necessary condition is not a guarantee. This is the classic "only if" trap.
• D — ✗ Wrong. Too strong and unsupported. Only one group failed, and the passage explains why.

Worked example 3 — Contrast logic

Among mammals that live in cold climates, larger body size is common, since a large body loses heat more slowly than a small one. The arctic fox, however, is smaller than many fox species that live in warmer regions. Researchers studying the arctic fox found that it has extremely thick fur, short legs, short ears, and a short muzzle, all of which reduce the amount of body surface that loses heat. Thus, the arctic fox's ability to survive extreme cold most likely ______

Question: Which choice most logically completes the text?

• A) shows that body size has no effect on heat loss in any mammal.
• B) depends on its larger body size compared with foxes in warmer regions.
• C) results from its habit of moving to warmer regions every winter.
• D) depends more on features such as its fur and body shape than on large body size.

Answer: D

• A — ✗ Wrong. Too strong. One exception does not cancel a general rule for all mammals.
• B — ✗ Wrong. Contradicts the passage: the arctic fox is SMALLER than many warm-climate foxes.
• C — ✗ Wrong. Outside information. The passage never mentions migration.
• D — ✓ Correct. The contrast word "however" tells us size cannot be the explanation; the next sentence gives other heat-saving features. D joins these two facts.

Worked example 4 — History: what the evidence can and cannot show

Historians have used the surviving letters of Hassan al-Tajir, a merchant in eighteenth-century Cairo, to describe daily life in his household. Yet almost all of the letters were written to business partners in other cities, and they deal mainly with prices, shipments, and debts; al-Tajir mentions his wife and children in only a handful of brief lines. Historians who rely on these letters to describe his household ______

Question: Which choice most logically completes the text?

• A) should conclude that al-Tajir had little contact with his family.
• B) know more about his family life than about his business.
• C) may be missing important information about his family life.
• D) should stop using the letters as a source for any historical question.

Answer: C

• A — ✗ Wrong. Too strong. Few mentions in BUSINESS letters do not show little contact; the letters had another purpose.
• B — ✗ Wrong. Reversed. The letters are mostly about business, so historians know more about his business.
• C — ✓ Correct. The gap: the letters were written for business, so they say little about the home. Using them to describe the household is therefore likely to leave things out.
• D — ✗ Wrong. Too extreme. The letters are still very useful for his trade; the problem is only with family life.

Practice

All pages in this course

Start here

• The Digital SAT: Complete Overview
• Time Strategy and How to Attack Every Question

Craft and Structure

• Words in Context
• High-Value Vocabulary for SAT Reading and Writing
• Text Structure and Purpose
• Cross-Text Connections

Information and Ideas

• Central Ideas and Details
• Command of Evidence: Textual
• Command of Evidence: Quantitative
• Inferences

Standard English Conventions

• Sentence Boundaries
• Commas and Extra Information
• Colons, Dashes and Semicolons
• Subject–Verb Agreement
• Pronouns
• Verb Tense, Aspect and Finiteness
• Modifiers, Parallel Structure and Comparisons
• Plurals and Possessives

Expression of Ideas

• Transitions
• Rhetorical Synthesis (Student Notes)

Full practice tests

• Digital SAT Reading and Writing — Practice Test 1
• Digital SAT Reading and Writing — Practice Test 2
• Digital SAT Reading and Writing — Practice Test 3