A passage describes a study that compared two cooling materials. The missing sentence sits after the method and before the results. One option repeats materials three times. Another explains how the temperatures were measured. Keyword overlap favors the first; passage structure favors the second.
That is the decision in Complete the Passage: choose the sentence whose references, time sequence, and discourse job fit the gap. A sentence can discuss the same topic and still belong somewhere else—or nowhere at all.
Duolingo’s current official description places Complete the Passage inside Interactive Reading. You choose the best sentence to fill a gap in a passage. This guide stays narrower than the general DET Interactive Reading guide: it focuses only on sentence fit, not the other question types in the set.
For connected preparation, use the DET vocabulary practice hub and Exam English hub. Every passage and option below is original practice. None is recalled or predicted test content.
Fit has three layers
The correct sentence must fit all three layers:
- Reference: pronouns and demonstratives must point to something recoverable.
- Chronology: events and stages must occur in a coherent order.
- Discourse role: the sentence must do the job the gap requires—define, explain, contrast, exemplify, report a result, or conclude.
Topic similarity is only a preliminary filter. Several options may contain the passage’s nouns. The winner must also connect backward and forward.
Read both seams
Call the sentence before the gap the left seam and the sentence after it the right seam.
The team placed identical containers in sun and shade. [GAP] The readings were then averaged for each location.
The left seam establishes two conditions. The right seam refers to the readings and says they were averaged then. A fitting sentence must introduce readings before averaging and should occur after placement.
Temperature was recorded every ten minutes for two hours.
This fits both seams. An option such as “Shade is valuable in many public parks” shares the topic but does not create the readings that the next sentence presupposes.
Reference: every pointer needs a target
Watch for this, these, such, it, they, the former, the latter, and definite noun phrases such as the change or the finding.
Local volunteers catalogued 600 photographs. [GAP] This digital record was later made available to schools.
The phrase This digital record requires the missing sentence or the previous sentence to establish a digital record. A strong option is:
They entered the date, location, and subject of each image into an online database.
Now this digital record points naturally to the database. An option about volunteers receiving photography lessons does not create the required referent.
Reject an option whose own pronouns lack antecedents. “This solved the problem immediately” cannot fit if no problem or solution has been introduced.
Chronology: find the stage of the process
Time markers make some choices impossible:
- initially, first, before establish an early stage;
- next, then, afterward advance a sequence;
- eventually, finally signal a later outcome;
- verb tenses and completed actions also locate events.
Researchers first interviewed residents about noise. [GAP] Finally, they compared the measurements with the interview responses.
The gap likely contains an intermediate collection step:
Next, they installed sound meters at six locations for one week.
An option stating the final conclusion would appear too early, before the evidence was compared. An option describing recruitment could belong before the interviews, not after them.
Do not assume every passage is chronological. An argumentative paragraph may be organized by claim and support instead. Use time order only when the text establishes it.
Discourse role: what work is missing?
Ask what the surrounding sentences are doing.
Definition to example
Some animals are crepuscular, meaning they are most active around dawn and dusk. [GAP] Rabbits, for instance, often feed during these low-light periods.
The gap should bridge the definition to the example, perhaps by explaining an advantage of low-light activity. A second definition of rabbits would compete with the right seam’s example marker.
Claim to evidence
The revised sign system reduced confusion among first-time visitors. [GAP] In exit surveys, 78 percent found their destination without asking staff for help, compared with 52 percent before the change.
The right seam is evidence. The gap could introduce the evaluation: “The museum tested the system for six weeks before assessing visitor experience.” A sentence announcing an unrelated benefit would interrupt claim-to-evidence movement.
Understanding is only the first step.
Lyra Practice helps you retrieve and use high-value workplace expressions in realistic situations until they feel natural.
Start a practice session →Problem to response
The wetland path flooded after moderate rain. [GAP] As a result, visitors could use the route during most of the rainy season.
The result presupposes an intervention. “Workers raised the path on a bed of permeable gravel” supplies it. “Wetlands support diverse species” shares the setting but cannot cause the stated access result.
Worked item
Read the passage and choose the missing sentence.
A town library wanted more residents to borrow tools from its small lending collection. Staff first surveyed people who had registered but never borrowed an item. Many respondents said they did not know what the collection contained. [GAP] During the next month, first-time tool loans increased, although the library did not claim that the display alone caused the change.
A. Tools can be expensive for households that need them only once.
B. In response, staff placed photographs and plain-language descriptions of every available tool near the entrance.
C. The library had replaced its roof two years earlier.
D. These respondents returned all borrowed tools on time.
Answer: B.
Reference: “In response” points to the knowledge problem in the previous sentence.
Chronology: the display is installed after the survey and before the following month’s loan count.
Discourse role: it supplies the intervention that the result evaluates.
A is topically relevant but has no role in this problem-response-result sequence. C is unrelated. D misuses These respondents by claiming they borrowed tools even though the passage says they had never done so.
Controlled practice 1: reference fit
Marine biologists photographed the same section of reef each month. They labeled every visible colony and stored the images in chronological order. [GAP] It allowed the team to distinguish sudden damage from gradual seasonal change.
A. This visual record showed how individual colonies changed over time.
B. Coral reefs occur in warm and cold waters.
C. They were expensive, so the colony moved away.
Answer: A. This visual record names the ordered image collection, and It in the next sentence refers back to that record. B offers a general fact but leaves It without a sensible antecedent. C has incoherent references and invents movement by a colony.
Controlled practice 2: chronology fit
A research team wanted to test whether a new lid reduced heat loss from reusable cups. First, they filled identical cups with water at the same temperature. [GAP] Finally, they compared the average temperature drop in each group.
A. Next, they covered half the cups with the new lid and measured every cup after thirty minutes.
B. The new lid became popular after the findings were published.
C. Reusable cups are sold in many colors.
Answer: A. It supplies the treatment and measurement between setup and comparison. B jumps beyond publication, which has not occurred. C has no procedural role.
Controlled practice 3: discourse role
Small shops on Harbor Street produced large amounts of cardboard waste. Individual shops lacked space to store enough cardboard for economical collection. [GAP] Consequently, collection costs per shop fell, and less cardboard entered the general waste stream.
A. Cardboard is usually brown but can be printed in many colors.
B. The shops therefore shared one locked storage container and arranged a joint weekly pickup.
C. Several shop owners preferred glass display shelves.
Answer: B. The paragraph moves from problem to collective response to consequence. The connector Consequently requires a cause, which B supplies.
Distractor patterns
The keyword echo
An option repeats several nouns but contributes the wrong relationship. A passage about urban trees may include a distractor defining forests. Shared vocabulary does not guarantee local coherence.
The true but misplaced fact
The sentence may be reasonable and relevant yet belong earlier or later. A conclusion cannot normally precede the method that supports it.
The orphan reference
An option begins “This approach” when no approach has appeared, or the next sentence says “these results” when the option introduced no results.
The reversed cause
The option mentions both events but presents the result as the cause. Track connectors such as because, therefore, and as a result precisely.
The scope jump
The passage reports one town, one study, or one month. A distractor suddenly claims that the finding is universal. Sentence fit includes claim size.
A reliable solving routine
- Read the entire passage once.
- Summarize the gap’s likely job in a few words: “method step,” “response to problem,” or “example.”
- Inspect pronouns and definite phrases on both seams.
- Mark any chronological constraint.
- Test each option against both seams, not only the sentence before the gap.
- Reread the full passage with your choice inserted.
If two options seem topical, state why each connects forward. The correct option usually satisfies a requirement created by the next sentence, such as an antecedent, cause, measurement, or contrast.
Common mistakes
- Counting repeated words instead of tracking relations.
- Reading only the left seam.
- Accepting a true statement that has no paragraph-level job.
- Ignoring a pronoun with no clear antecedent.
- Moving a result before its method or a response before its problem.
- Choosing a universal claim after narrowly bounded evidence.
- Adding outside knowledge instead of using the passage.
Final mixed item
A school replaced disposable cafeteria trays with washable ones. Administrators expected less waste, but they also wanted to measure the extra resources used for washing. [GAP] The figures showed lower solid waste but higher water use, allowing the school to describe the trade-off rather than claiming an unqualified environmental benefit.
A. For eight weeks, staff recorded both the number of trash bags and the water consumed by the industrial dishwasher.
B. Washable trays are generally stronger than thin disposable trays.
C. This proved that washable products always protect the environment.
Answer: A. The next sentence’s figures requires measurements. A introduces two figures matching the two sides of the trade-off and fits between the evaluation goal and results. B creates no figures. C is both premature and broader than the bounded evidence.
For fresh reading decisions with immediate feedback, try Lyra Practice.
Sources
Related
- DET Interactive Reading: connect ideas across the passage
- DET Read and Complete word families
- DET Fill in the Blanks vocabulary in context
- DET Read and Select vocabulary
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