C1 Advanced · Reading & Use of English · Part 3

C1 Word Formation Practice (Free)

Build more flexible word-family control. Decide which form carries the intended meaning, including negative and plural forms that are easy to overlook.

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This exercise, its explanations and the downloadable PDF are in English.

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Testing the air around us

Use the word in capitals beside each gap to form one word that fits the passage. Consider the part of speech and whether the meaning needs a negative prefix.

Original, independent teaching material. No account needed. The result counts correct answers in this sample, not exam marks.

A neighbourhood group bought inexpensive sensors to measure local air pollution. Before publishing the results, they asked a university to check the equipment's Gap 1RELY. The first readings were Gap 2CONSIST: two sensors placed beside each other reported sharply different figures. A direct Gap 3COMPARE with a laboratory instrument confirmed that one sensor needed adjusting.

The researchers explained that a single reading was Gap 4LIKELY to provide a useful picture of conditions over a whole month. Instead, they recommended a Gap 5SYSTEM approach, with measurements taken at regular intervals in the same locations. They also warned against confusing a small numerical difference with a change of practical Gap 6SIGNIFY.

The group welcomed this advice. Full Gap 7DISCLOSE of the method would allow other residents to understand how the figures had been collected. Although some early results remained Gap 8CONCLUDE, the project had already taught its volunteers something valuable: collecting data was only the beginning of a careful investigation, not a substitute for one.

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Answers and explanations

Read the reason behind each answer, then return to the text and find the evidence yourself.

Question 1: Reveal answer and explanation

Answer: reliability

RELY → reliability. “Check the equipment's reliability” needs a noun after the possessive. Reliability is its ability to give trustworthy results; reliable is an adjective and cannot fill that noun position. The family changes rely to reliable, then reliability: notice the -i- and the ending -ability.

Question 2: Reveal answer and explanation

Answer: inconsistent

CONSIST → inconsistent. “The first readings were inconsistent” needs an adjective describing the readings. “Sharply different figures” from neighbouring sensors shows disagreement, so the negative prefix in- is essential. Consistency is a noun; consistent would contradict the evidence.

Question 3: Reveal answer and explanation

Answer: comparison

COMPARE → comparison. “A direct comparison with a laboratory instrument” requires a singular countable noun after a direct. Comparison names the act of checking the two instruments against each other. Comparative is normally an adjective here and would leave the noun missing; comparing does not fit a direct ... with in this sentence.

Question 4: Reveal answer and explanation

Answer: unlikely

LIKELY → unlikely. “A single reading was unlikely to provide a useful picture ... over a whole month.” The recommendation for repeated measurements establishes the negative meaning. Add un- to likely; likelihood would require a different structure. Unlikely to + verb means not expected to happen.

Question 5: Reveal answer and explanation

Answer: systematic

SYSTEM → systematic. “A systematic approach” needs an adjective before the noun. “At regular intervals in the same locations” describes an organised method. Systemic means affecting an entire system and does not describe the step-by-step measurement procedure intended here.

Question 6: Reveal answer and explanation

Answer: significance

SIGNIFY → significance. “A change of practical significance” requires a noun after the adjective practical. Significance means importance: the researchers distinguish a measurable difference from one that matters. Significant is an adjective and would need to modify a noun rather than follow practical in this phrase.

Question 7: Reveal answer and explanation

Answer: disclosure

DISCLOSE → disclosure. “Full disclosure of the method would allow...” uses a noun phrase as the sentence's subject. Disclosure means making the procedure available for inspection. Disclosed is a participle and cannot be the head noun after full. Notice the ending -sure rather than an invented -ment form.

Question 8: Reveal answer and explanation

Answer: inconclusive

CONCLUDE → inconclusive. “Some early results remained inconclusive” needs an adjective after remained. Although introduces a contrast: results did not settle the scientific question, but volunteers learned something. Conclusive would reverse that meaning; conclusion is a noun. Form conclusive, then add in-.

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