Distinguish major ideas from minor details or examples.
核心知识
Tell apart the big-picture claim from the specific examples or details used to support it.
深入理解
Every passage has a hierarchy: the main idea sits on top, and supporting details, examples, and data sit underneath. SAT questions exploit the fact that students often confuse a vivid example for the main point.
Think of it this way: the main idea is the headline; supporting details are the article beneath it. If the passage argues that urban green spaces improve mental health, and then mentions a study in Tokyo where park visitors showed lower cortisol levels, the Tokyo study is a detail. The main idea is the broader claim about green spaces and mental health.
A useful test: ask "Could the author replace this detail with a different example and still make the same point?" If yes, it's a supporting detail, not the main idea.
分步讲解
- Read the passage and identify the broadest claim — this is usually the main idea.
- Notice which sentences provide evidence, data, or examples for that claim — these are supporting details.
- When evaluating answer choices, ask: "Does this choice capture the big point, or does it only describe one example?"
- If a choice can be "swapped out" for a different example without changing the passage's purpose, it's a detail, not the main idea.
- Choose the answer that sits at the right level of the hierarchy.
常见误解
- Picking the most specific or vivid answer — memorable examples feel important, but they serve the main idea, not replace it.
- Treating a statistic as the main point — numbers are almost always supporting evidence, not the central claim.
- Assuming the first sentence is always the main idea — sometimes the opening provides background, and the main idea appears mid-passage.
示例解析
The field of biomimicry — designing technology inspired by natural organisms — has produced innovations ranging from Velcro (modeled on burdock burrs) to bullet-train noses (shaped like kingfisher beaks). More recently, engineers have studied the structure of shark skin, which features tiny tooth-like scales called denticles that reduce drag in water. Swimsuit manufacturers incorporated this texture into competition suits, and shipping companies are now testing similar coatings to reduce fuel consumption in cargo vessels.
Which choice best states the main idea of the text?
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