Numerical answer
Five sentences related to a common theme are given below. Four of them can be sequenced into a coherent paragraph, while one does not fit. Identify the sentence that does NOT fit (enter its number).
1. Antarctic ice cores allow scientists to reconstruct atmospheric composition going back hundreds of thousands of years, trapped as tiny bubbles within compacted snow layers.
2. Each layer of ice corresponds roughly to a year of snowfall, functioning much like a tree ring in recording the conditions under which it formed.
3. The Arctic, by contrast, has comparatively little multi-year ice left, having lost much of its oldest layers to accelerating summer melt.
4. By counting these layers and analysing the trapped air, researchers can track carbon dioxide and methane concentrations across ice ages long before direct measurement was possible.
5. This long, undisturbed record is precisely what makes Antarctic cores so valuable for understanding the planet's climate history over deep time.
1. Antarctic ice cores allow scientists to reconstruct atmospheric composition going back hundreds of thousands of years, trapped as tiny bubbles within compacted snow layers.
2. Each layer of ice corresponds roughly to a year of snowfall, functioning much like a tree ring in recording the conditions under which it formed.
3. The Arctic, by contrast, has comparatively little multi-year ice left, having lost much of its oldest layers to accelerating summer melt.
4. By counting these layers and analysing the trapped air, researchers can track carbon dioxide and methane concentrations across ice ages long before direct measurement was possible.
5. This long, undisturbed record is precisely what makes Antarctic cores so valuable for understanding the planet's climate history over deep time.
Show answer and solution
Answer: 3
Sentences 1, 2, 4 and 5 form a coherent account of how Antarctic ice cores record climate history (formation of layers, how they're read, why they're valuable). Sentence 3 shifts topic to the Arctic's loss of multi-year ice — a different, contrasting subject that breaks the logical flow of the paragraph about Antarctic ice cores.
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