Unit 4
Sentence Gap
About this unit
In the OC Reading paper, a Sentence Gap question presents a multi-paragraph informational passage with 6 sentences removed. Seven sentences are provided — six belong in the passage and one is a distractor that does not fit anywhere. For each gap, marked with a letter (A–F), you must choose which of the seven sentences belongs there.
Unlike Cloze, where you fill in single words, Sentence Gap requires you to work with whole ideas. The correct sentence must fit the paragraph's topic (it should be about the right subject) AND its logic (it should follow naturally from the sentence before it and lead into the sentence after it). Getting both right is the key skill.
The distractor sentence is written to sound as if it belongs somewhere in the passage. Learning to spot why it does not fit any gap — and why the correct sentence fits better — is as important as finding the right answer.
What types of questions will you face?
- 1Logical flow gaps — the removed sentence must continue the logic of the previous sentence AND prepare for the following sentence. The surrounding sentences almost always contain a pronoun or signal word that points to what the gap must contain.
- 2Topic bridge gaps — the sentence links two ideas that belong to the same paragraph but are not explicitly connected. The gap sentence acts as a bridge, and the paragraph feels incomplete or jumpy without it.
- 3Specific detail gaps — the sentence provides a concrete example, statistic, or observation that the surrounding general statement sets up. Look for a general claim immediately before the gap — the correct sentence usually provides the evidence or elaboration.
- 4Contrast and exception gaps — a contrast marker in the sentence after the gap ("however", "yet", "despite", "but") signals that the gap sentence must introduce the idea that is then being contrasted. Removing the contrast marker as a clue makes this type much harder.
Skills you will build
- Reading both neighbours — before looking at the 7 options, read the sentence immediately before the gap AND the sentence immediately after it. Your job is to find a sentence that connects logically to BOTH. Testing a sentence against only one neighbour is the most common error.
- Following transition signals — look for signal words and pronouns adjacent to the gap: "this", "they", "such", "however", "therefore". These words tell you what the gap sentence must contain or introduce. The gap sentence is usually the referent that the following pronoun or demonstrative points back to.
- Tracking paragraph topic — identify the main topic of each paragraph before attempting its gap. Any correct sentence must stay on that topic. Reject sentences that introduce an unrelated idea, even if they sound interesting or are mentioned elsewhere in the passage.
- Eliminating the distractor last — after placing five sentences confidently, the distractor becomes clear: it does not connect properly to any remaining gap. If you find a sentence that seems like it could fit two different gaps, you are probably looking at a distractor.
By the end of this unit, you will be able to
- Identify the topic of each paragraph before attempting to fill its gap.
- Use signal words and pronouns in adjacent sentences to narrow the correct sentence to 2–3 candidates.
- Test each candidate against both the preceding AND following sentence to confirm the best fit.
- Identify the distractor sentence by checking that it cannot connect properly to any unfilled gap.
Difficulty profile
Sentence Gap is consistently the hardest question type in OC Reading. The passage is long, and the 6 decisions are connected — a wrong answer to Gap A can make Gap B harder to solve. Most students lose marks not because the topic is difficult, but because they test a candidate sentence against only one neighbour rather than both. The distractor catches students who match by topic alone rather than by logical connection. Confident students work through the easiest gaps first (where both neighbours are strong signals), leaving the hardest gaps until they have already eliminated most of the sentences.
Exam tip: Sentence Gap
Step 1: Read the whole passage before attempting any gap
Read the entire passage from start to finish before you look at the 7 sentences. You need to understand each paragraph's topic and how the paragraphs connect to each other. Jumping straight to Gap A without reading the whole text means you are choosing sentences without context.
Step 2: Identify the topic of each paragraph
Write one word beside each paragraph (or hold it in your head): What is this paragraph about? Every correct sentence must stay on that topic. If a candidate sentence introduces an idea that belongs to a different paragraph, it is wrong — even if it sounds interesting.
Step 3: Read both neighbours of the gap
For each gap, read the sentence immediately before it AND the sentence immediately after it. This is the most important step. The correct sentence must connect logically to BOTH. Common mistakes:
- Testing only the sentence before the gap
- Choosing a sentence that fits the topic but does not connect to the following sentence
- Ignoring signal words like "this", "they", "such", "however"
Step 4: Follow the signal words
Look for pronouns and transition words adjacent to the gap:
- "This..." or "Such..." after the gap → the gap sentence must introduce the thing being referred to
- "They..." or "It..." after the gap → the gap sentence probably introduces the subject of those pronouns
- "However..." or "Yet..." after the gap → the gap sentence must introduce the idea being contrasted
- "Therefore..." or "As a result..." after the gap → the gap sentence must introduce the cause
Step 5: Place easy gaps first, hard gaps last
Work through the gaps where both neighbours provide strong signals. Leave ambiguous gaps until you have eliminated more sentences. The distractor often becomes obvious once you have placed 5 sentences confidently.
Spotting the distractor
The distractor is written to sound relevant. It will often:
- Be about the right general topic but from the wrong angle
- Sound like it could fit two different gaps but does not fit either perfectly
- Introduce information that belongs to a different part of the passage
After placing your 5 most confident answers, check the remaining sentence against the remaining gap: if it still does not quite connect to both neighbours, it is the distractor.
Time target: the passage is long — aim to spend 4–5 minutes total, reading once quickly and then working gap by gap.
Sample Questions
Read the extract below, then answer the questions.
The Long Journey of the Monarch
Every autumn, millions of orange and black monarch butterflies leave their summer homes in Canada and the United States and begin flying south. Their destination is a small area of forest in central Mexico, over four thousand kilometres away. (A) Scientists have studied this migration for decades, and it continues to surprise them.
Unlike birds, monarch butterflies cannot store enough energy to complete the journey in one go. They stop to feed on flowers along the way, refuelling on nectar before pressing on. (B) A single butterfly may travel up to one hundred kilometres on a warm, sunny day.
When the monarchs finally arrive in Mexico, they do something spectacular. Millions of butterflies settle in clusters on the branches of oyamel fir trees, their wings folded and overlapping like layers of autumn leaves. (C) Local communities have come to call this event the arrival of the monarchs, and it has been celebrated for generations.
What makes the monarch's journey even more remarkable is that no individual butterfly completes the full round trip. The butterflies that travel south in autumn will overwinter in Mexico, then begin flying north in spring. (D) In this way, it may take four or five generations to complete one full cycle.
In recent decades, the monarch population has declined sharply. Milkweed — the only plant on which monarchs lay their eggs and which their caterpillars eat — has been destroyed across much of its range. (E) Without milkweed, there can be no monarchs.
Conservation efforts are now underway across North America. Schools, farmers, and government agencies are planting milkweed corridors to restore the butterflies' pathway north. (F) Scientists hope that, with continued effort, the monarch's great migration will continue for generations to come.
Choose from these sentences — one does not belong anywhere:
1. They use warm air currents, called thermals, to rise high into the sky before gliding southward, conserving energy for the journey ahead.
2. The forest becomes so dense with butterflies that the air itself trembles with the movement of their wings.
3. They will lay their eggs on milkweed plants as they move northward, and it is their offspring that continue the journey.
4. Herbicides used in modern farming have cleared the plant from millions of hectares of farmland and roadsides where it once flourished.
5. In some areas, early results suggest that the butterfly population is beginning to stabilise after years of decline.
6. Despite travelling such vast distances, they navigate to the same mountain forests — and sometimes even the same individual trees — as their ancestors the year before.
7. Tagged butterflies have helped researchers discover that the same family of trees in Mexico may have hosted monarchs for over a century.
Which sentence best fits gap (A)?
- ADespite travelling such vast distances, they navigate to the same mountain forests — and sometimes even the same individual trees — as their ancestors the year before.
- BTagged butterflies have helped researchers discover that the same family of trees in Mexico may have hosted monarchs for over a century.
- CThe forest becomes so dense with butterflies that the air itself trembles with the movement of their wings.
- DThey use warm air currents, called thermals, to rise high into the sky before gliding southward, conserving energy for the journey ahead.
Decided on your answer? Check how you went below.
Which sentence best fits gap (B)?
- AThe forest becomes so dense with butterflies that the air itself trembles with the movement of their wings.
- BThey use warm air currents, called thermals, to rise high into the sky before gliding southward, conserving energy for the journey ahead.
- CIn some areas, early results suggest that the butterfly population is beginning to stabilise after years of decline.
- DTagged butterflies have helped researchers discover that the same family of trees in Mexico may have hosted monarchs for over a century.
Decided on your answer? Check how you went below.
Which sentence best fits gap (C)?
- ATagged butterflies have helped researchers discover that the same family of trees in Mexico may have hosted monarchs for over a century.
- BHerbicides used in modern farming have cleared the plant from millions of hectares of farmland and roadsides where it once flourished.
- CThe forest becomes so dense with butterflies that the air itself trembles with the movement of their wings.
- DThey will lay their eggs on milkweed plants as they move northward, and it is their offspring that continue the journey.
Decided on your answer? Check how you went below.
Which sentence best fits gap (D)?
- ATagged butterflies have helped researchers discover that the same family of trees in Mexico may have hosted monarchs for over a century.
- BHerbicides used in modern farming have cleared the plant from millions of hectares of farmland and roadsides where it once flourished.
- CIn some areas, early results suggest that the butterfly population is beginning to stabilise after years of decline.
- DThey will lay their eggs on milkweed plants as they move northward, and it is their offspring that continue the journey.
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Which sentence best fits gap (E)?
- AIn some areas, early results suggest that the butterfly population is beginning to stabilise after years of decline.
- BHerbicides used in modern farming have cleared the plant from millions of hectares of farmland and roadsides where it once flourished.
- CTagged butterflies have helped researchers discover that the same family of trees in Mexico may have hosted monarchs for over a century.
- DThey will lay their eggs on milkweed plants as they move northward, and it is their offspring that continue the journey.
Decided on your answer? Check how you went below.
Which sentence best fits gap (F)?
- AHerbicides used in modern farming have cleared the plant from millions of hectares of farmland and roadsides where it once flourished.
- BThey will lay their eggs on milkweed plants as they move northward, and it is their offspring that continue the journey.
- CTagged butterflies have helped researchers discover that the same family of trees in Mexico may have hosted monarchs for over a century.
- DIn some areas, early results suggest that the butterfly population is beginning to stabilise after years of decline.
Decided on your answer? Check how you went below.
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