Choose a, b, c or d as the best answer.4. Which statement best summarises the main idea of this paragraph?

Question

BlackTom AI · Accepted Answer

The correct answer is B: Carbon taxes should be used to reduce greenhouse gases.

1) Relevant knowledge points and concepts
- Main idea (thesis) vs supporting details: the main idea is the central claim or recommendation the paragraph advances, not a background fact or an example.
- Identifying author’s purpose: if the paragraph argues for a policy or action, the main idea will usually be the recommended action or position.
- Distinguishing scope: compare broad statements (general problem), causal claims (what causes it), and prescriptive claims (what should be done).

2) Step-by-step reasoning
- Step 1 — determine the paragraph’s focus: the choices show the paragraph concerns climate/global warming and a solution. If the paragraph argues for a response, the thesis is prescriptive.
- Step 2 — match each option to possible roles: (a) states the problem’s seriousness (background); (c) claims cause (fact); (d) states an observed effect (fact/result); (b) recommends a specific policy (prescriptive thesis).
- Step 3 — because the prompt asks for the best summary of the main idea, preference goes to the option that captures the author’s central claim rather than a supporting fact.

3) Calculations / intermediate steps
- Not applicable (no numeric work required). The “intermediate steps” are the logical matches in Step 2 above.

4) Why the correct answer is correct
- Option B is prescriptive and states a concrete solution: using carbon taxes to reduce greenhouse gases. If the paragraph’s thrust is to argue for policy, this captures the central thesis and is therefore the main idea.

5) Why the other options are incorrect
- A: “Global warming is an enormous and serious global problem” is a background statement, not a policy recommendation; it could be a supporting sentence.
- C: “Carbon pollution is the main contributor to climate change” is a causal fact; it supports an argument but is not the overarching point.
- D: “Climate change has impacted on global temperatures” is a narrow factual observation, not the paragraph’s central claim.

6) Conclusion
Therefore the main idea is best summarized by option B, which matches the provided correct answer: b. Carbon taxes should be used to reduce greenhouse gases.

Choose a, b, c or d as the best answer.4. Which statement best summarises the main idea of this paragraph?单项选择题

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