Read the following passage.
A. Permafrost is ground whose temperature stays at or below freezing for two or more years in a row. It lies beneath at least 40 per cent of Canada's land, mainly in the Arctic islands, Yukon, the Northwest Territories and Nunavut. Above it sits the active layer, a band of soil that thaws each summer and freezes again each winter. Much of this frozen ground holds a great deal of ice, and in some places ice makes up as much as 80 per cent of it. While it stays frozen, the ground is as hard as concrete, but when it melts, the surface can collapse.
B. Thaw leaves clear marks on the land. Where ground ice melts, the surface sinks and ponds or small lakes form, creating an uneven terrain known as thermokarst. In forests, roots grow so weak that trees tilt and fall against one another, a pattern called a drunken forest. On slopes, thawing soil can give way in large slumps, and heavier rainfall appears to be closely linked to this slumping. Over the last 50 years in northern Quebec, permafrost mounds have been lost and thermokarst ponds have grown. In the southern Northwest Territories, forest die-off has been blamed on thawing ground and subsidence.
C. Heated homes usually stand on piles with an air gap underneath, so that warmth from inside does not reach the soil. Engineers may replace the soil under a road with gravel so that water drains away, and some experts recommend painting roads white to keep them cooler. In Inuvik, water and sewer lines cannot go underground. They run through insulated boxes called utilidors, which keep the water from freezing and the permafrost from thawing. In Dawson City, some buildings from the gold rush of 1896 to 1899 were damaged when heat from inside thawed the ground below.
D. The frozen ground is now warming. Temperatures measured in boreholes up to 20 metres deep have risen across northern Canada, faster in the high Arctic than in the central Mackenzie Valley. In the Mackenzie Valley, the layer that thaws each summer has thickened by about 10 per cent since 2000. Thaw also affects the climate. When the frozen remains of plants and animals thaw, they decay and give off carbon dioxide or methane. Permafrost is thought to hold about 1,400 gigatons of carbon, 2.5 times the amount now in the atmosphere. As it thaws, pipelines, buildings, roads and airports face structural damage that will be costly to repair.
E. Not given in any of the above paragraphs.
Decide which paragraph, A to D, has the information given in each statement below. Select E if the information is not given in any of the paragraphs.
AI explanationShows the answer. Tap to open.
Correct Answer: C
Why this is correct: Look at Paragraph C. Heated homes usually stand on piles with an air gap underneath. The gap stops warmth from inside reaching the soil. So the houses are lifted up to keep their heat away from the ground.
Passage Reference: Heated homes usually stand on piles with an air gap underneath, so that warmth from inside does not reach the soil.
Tips: Paragraph D also mentions buildings. Pick the paragraph that shows how a house is kept off the soil.
Why the other options are wrong:
- A: Paragraph A tells you what permafrost is and that the surface can collapse when ice melts. It does not explain how houses are built.
- B: Paragraph B describes ponds, leaning trees and slumps on the land. Homes and their heating do not come up.
- D: Paragraph D lists buildings among the things that thaw may damage. It never shows a way of building that protects the ground.
- E: Go back to the first sentence of Paragraph C. The piles and air gap under heated homes are there.
Correct Answer: B
Passage Reference: On slopes, thawing soil can give way in large slumps, and heavier rainfall appears to be closely linked to this slumping.
Why this is correct: The clue is in Paragraph B. On slopes, thawing soil can give way in large slumps. Heavier rainfall appears to be closely linked to this slumping. Rain is wet weather, and slopes are hillsides.
Tips: Find the part about hillsides sliding down after a thaw. Then check what kind of weather the text connects with it.
Why the other options are wrong:
- A: Paragraph A mentions the surface collapsing when ground ice melts. It says nothing about rain or slopes.
- C: Paragraph C talks about gravel that lets water drain away under roads. That is a building method, not a reason hillsides slide.
- D: Paragraph D reports warming ground and carbon release. Weather that brings slopes down is not part of it.
- E: Heavier rain is linked to slumping on slopes in Paragraph B, so the idea is there.
Correct Answer: E
Passage Reference: Permafrost is thought to hold about 1,400 gigatons of carbon, 2.5 times the amount now in the atmosphere.
Why this is correct: Be careful here. Paragraph D names the high Arctic and the Mackenzie Valley, but only to compare how fast the ground warms. Its carbon figure is for all permafrost together. No paragraph splits the carbon by region.
Tips: The statement puts the coldest Arctic regions beside the Mackenzie Valley. Read what the text tells you about each region, and compare it with the carbon claim.
Why the other options are wrong:
- A: Paragraph A lists the northern areas where permafrost lies. Carbon is not mentioned at all.
- B: Paragraph B describes thaw marks in Quebec and the Northwest Territories. It gives no carbon amount for any area.
- C: Paragraph C is about how people build in the North. It never talks about carbon.
- D: Paragraph D comes nearest. It compares warming speed in the two regions and gives one carbon total, about 1,400 gigatons. It does not say which region holds more.
Correct Answer: C
Passage Reference: They run through insulated boxes called utilidors, which keep the water from freezing and the permafrost from thawing.
Why this is correct: Look at Paragraph C. In Inuvik, water and sewer lines run through insulated boxes called utilidors. These boxes keep the water from freezing. They also keep the permafrost from thawing, so they protect both.
Tips: Paragraph D also mentions pipelines. Here you want pipes that are built to help, not pipes in danger.
Why the other options are wrong:
- A: Paragraph A explains what permafrost is and where it lies. It names no single town and no pipes.
- B: Paragraph B talks about ponds and dying forests in some regions. Water supply lines are not discussed.
- D: Paragraph D lists pipelines among things thaw may damage. It does not describe pipes that protect the ground.
- E: The text does describe this. Read about the utilidors of Inuvik in Paragraph C.
Correct Answer: A
Passage Reference: Much of this frozen ground holds a great deal of ice, and in some places ice makes up as much as 80 per cent of it.
Why this is correct: Paragraph A has the answer. In some places, ice makes up as much as 80 per cent of the frozen ground. If most of the ground is ice, it holds more ice than soil.
Tips: Look for a percentage about ice in the ground, not about warming or carbon.
Why the other options are wrong:
- B: Paragraph B talks about ground ice melting and the surface sinking. It gives no share of ice in the ground.
- C: Paragraph C covers piles, gravel and utilidors. It does not say how much ice the ground holds.
- D: Paragraph D gives a 10 per cent change in the thaw layer and a carbon figure. Neither one is about ice content.
- E: The text gives this detail. The figure of up to 80 per cent ice is in Paragraph A.
Correct Answer: E
Passage Reference: Engineers may replace the soil under a road with gravel so that water drains away, and some experts recommend painting roads white to keep them cooler.
Why this is correct: Be careful with Paragraph C. Some experts recommend painting roads white to keep them cooler. That is only advice. The text never says any highway was painted after that.
Tips: Advice and a finished job are different things. Check if the text says the work was really done.
Why the other options are wrong:
- A: Paragraph A describes permafrost and how hard it is while frozen. Roads do not appear.
- B: Paragraph B is about thermokarst, drunken forests and slumps. It says nothing about road surfaces.
- C: The advice to paint roads white is in Paragraph C, but the paragraph stops there. No road is reported as painted.
- D: Paragraph D warns that roads may be damaged by thaw. It does not mention any change to their colour.
Correct Answer: D
Passage Reference: In the Mackenzie Valley, the layer that thaws each summer has thickened by about 10 per cent since 2000.
Why this is correct: Check Paragraph D. In the Mackenzie Valley, the layer that thaws each summer has thickened by about 10 per cent since 2000. A thicker layer means summer thaw now reaches deeper than it did then.
Tips: Paragraph A also mentions the layer that thaws each summer. Find where it is said to have changed.
Why the other options are wrong:
- A: Paragraph A explains the active layer that thaws every summer. It does not say its depth has changed.
- B: Paragraph B reports 50 years of change in northern Quebec. Those changes are about mounds and ponds, not how deep the thaw goes.
- C: Paragraph C covers building methods and damage in Dawson City. No change in thaw depth is given.
- E: Paragraph D reports the thicker summer thaw layer in the Mackenzie Valley, so the idea does appear.
Correct Answer: E
Passage Reference: Over the last 50 years in northern Quebec, permafrost mounds have been lost and thermokarst ponds have grown.
Why this is correct: Paragraph B tells you that permafrost mounds have been lost in northern Quebec over the last 50 years. It reports what happened. It does not say who recorded it, and no university is named.
Tips: Ask yourself who did the recording. A text can report a change without naming anyone.
Why the other options are wrong:
- A: Paragraph A lists where permafrost lies in Canada. Quebec and its researchers are not part of it.
- B: The lost mounds in northern Quebec are reported in Paragraph B. Still, it never names the people who studied them.
- C: Paragraph C talks about engineers and experts on building. None of them studied land changes in Quebec.
- D: Paragraph D gives borehole temperatures and a carbon estimate. It does not say who studied the mounds in Quebec.
Correct Answer: A
Passage Reference: While it stays frozen, the ground is as hard as concrete, but when it melts, the surface can collapse.
Why this is correct: The last sentence of paragraph A describes the ground. While it stays frozen, it is as hard as concrete. When it melts, the surface can collapse. So it is very firm when frozen but can cave in after a thaw.
Tips: Check both parts of the idea: how firm the frozen ground is, and what a thaw can do to it.
Why the other options are wrong:
- B: Paragraph B shows the surface sinking after ice melts. It never says how hard the ground is while frozen.
- C: Paragraph C explains how builders protect the ground. It does not describe how strong frozen ground is.
- D: Paragraph D reports warming and likely damage to buildings and roads. The hardness of frozen ground is not mentioned.
- E: The text covers this. Paragraph A compares frozen ground with concrete and says it can collapse after melting.
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