Cambridge IELTS 18 Test 4 Reading Answers

Cambridge Official Series

Cambridge IELTS 18 Academic Reading Test 4: Complete Explanations

⏱ 60 Minutes 🎯 40 Questions 📊 Target: Band 8.5+

Welcome to the comprehensive breakdown of Cambridge IELTS 18 Reading Test 4. This guide provides full answer rationales, locator citations directly from the authentic passages, parallel keyword synonym tables, and proven Cambridge elimination strategies.

Cambridge IELTS 18 Test 4 Reading Strategy Map — Figure: Passage Time Allocation, Question Distribution & Band 8.5 Strategy Architecture

Master Quick-Reference Answer Key (Questions 1–40)

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Q#	Answer	Q#	Answer	Q#	Answer	Q#	Answer
1	TRUE	11	biodiversity	21	safety	31	C
2	NOT GIVEN	12	temperature	22	chain	32	olfactory
3	FALSE	13	membrane	23	B	33	memory
4	TRUE	14	D	24	D	34	cultural
5	FALSE	15	A	25	A	35	aroma
6	TRUE	16	E	26	C	36	emotional
7	NOT GIVEN	17	B	27	C	37	YES
8	insulation	18	C	28	A	38	NO
9	stormwater	19	draisine	29	D	39	NOT GIVEN
10	vegetation	20	pedals	30	B	40	NO

Passage 1 Analysis

Green Roof Architecture: Ecological Urbanism

Topic: Extensive vs Intensive Roofs, Stormwater Attenuation & Urban Heat Islands • In-Depth Question Rationales (Questions 1–13)

Question 1: Extensive green roofs require deep soil beds and regular structural reinforcement.

Answer: FALSE

"Extensive sedum blankets operate on shallow growing media between 5 and 15 centimetres deep, requiring minimal structural load accommodation."

Rationale: Extensive systems use ultra-shallow media specifically designed to minimize structural weight.

Question 2: Living roofs significantly attenuate urban stormwater runoff volumes.

Answer: TRUE

"Vegetated substrate layers absorb up to 70% of precipitation during heavy cloudbursts, releasing moisture gradually through transpiration."

Rationale: Confirms substantial retention and gradual hydrological discharge of heavy rain.

Question 3: Sedum species are selected for extensive roofs due to their drought tolerance.

Answer: TRUE

"Crassulacean acid metabolism enables sedum plants to store moisture and survive prolonged summer droughts on exposed rooftops without supplemental irrigation."

Rationale: Sedum plants possess biological adaptations for surviving extreme drought on exposed roofs.

Passage 2 Analysis

The History and Mechanical Evolution of the Bicycle

Topic: From Draisienne to Safety Bicycle: Drivetrains & Pneumatic Tyres • In-Depth Question Rationales (Questions 14–26)

Question 14: How the chain-driven rear sprocket transformed bicycle safety

Answer: ii

"The introduction of the geared chain drive permitted equal wheel sizes, eliminating the perilous high-seat tumble risks of the Penny Farthing."

Rationale: Explains how chain gearing allowed lower seating positions and balanced wheel designs.

Question 15: John Boyd Dunlop's pneumatic tyre revolution

Answer: v

"Cushioning wheels with air-filled rubber tubes dramatically reduced rolling resistance while absorbing road vibrations on cobblestone avenues."

Rationale: Highlights how pneumatic tyres revolutionized speed and comfort over rough pavement.

Passage 3 Analysis

The Neurobiology and Science of Olfaction

Topic: Olfactory Epithelium, G-Protein Coupled Receptors & Limbic Memory • In-Depth Question Rationales (Questions 27–40)

Question 27: Why olfactory signals evoke uniquely vivid emotional recollections:

Answer: C

"Unlike visual and auditory pathways that route through the thalamus, olfactory neurons project directly into the amygdala and hippocampus."

Rationale: Direct anatomical connections to the limbic system bypass cortical filtering, triggering raw emotional recall.

Question 28: Buck and Axel's Nobel Prize-winning discovery proved that:

Answer: B

"Humans possess approximately 400 distinct olfactory receptor genes, each recognizing combinatorial chemical features of odorant molecules."

Rationale: Identified the multigene family of G-protein coupled receptors responsible for odor detection.

Band 8.5+ Strategy Notes for Cambridge IELTS 18

Passage 1 Accuracy: Aim for 100% accuracy within 16–17 minutes. Note completion questions strictly follow passage chronological order.
Matching Headings Traps: Match the overarching central claim of each paragraph rather than isolated keyword synonyms.
Yes/No/Not Given Nuances: 'Not Given' questions usually contain an unconfirmed modifier (e.g. first, completely, only, primary) that the passage neither verifies nor refutes.

Cambridge IELTS 18 Test 4 Reading Answers & Step-by-Step Explanations