GRE阅读（RC）中推断题核心解题思路

推断题核心解题方法

推断题是 GRE 阅读（RC）的高频题型，约占所有阅读题的 70%，核心考查基于原文信息的严谨推导能力 —— 不同于现实生活中的 “合理猜测”，GRE 推断题要求答案 “必然为真” 或 “几乎必然为真”，无需额外假设，仅依赖原文信息即可验证。

（一）核心解题原则

优先通读全文，构建 “内容定位图（MOC）”：把握主旨（如本文核心是 “喷口动物群食物来源”）、分论点及细节位置，避免先读题再回文盲目定位；

严格依据原文，拒绝主观猜测：正确答案要么是原文信息的同义改写，要么是可严格求证的逻辑延伸，错误答案多为 “无中生有”“与原文矛盾” 或 “需额外假设”；

采用 “由外而内” 排除法：GRE 选项中通常至少有 2 个明显错误（如偏离主题、未提及关键词），先排除错误选项，再从剩余选项中锁定正确答案，提升解题效率。

（二）推断题题型分类

实战文章原文

The deep sea typically has a sparse fauna dominated by tiny worms and crustaceans, with an even sparser distribution of larger animals. However, near hydrothermal vents, areas of the ocean where warm water emerges from subterranean sources, live remarkable densities of huge clams, blind crabs, and fish.

Most deep-sea faunas rely for food on particulate matter ultimately derived from photosynthesis, falling from above. The food supplies necessary to sustain the large vent communities, however, must be many times the ordinary fallout. The first reports describing vent faunas proposed two possible sources of nutrition: bacterial chemosynthesis, production of food by bacteria using energy derived from chemical changes, and advection, the drifting of food materials from surrounding regions. Later, evidence in support of the idea of intense local chemosynthesis was accumulated: hydrogen sulfide was found in vent water; many vent-site bacteria were found to be capable of chemosynthesis; and extremely large concentrations of bacteria were found in samples of vent water thought to be pure. This final observation seemed decisive. If such astonishing concentrations of bacteria were typical of vent outflow, then food within the vent would dwarf any contribution from advection. Hence, the widely quoted conclusion was reached that bacterial chemosynthesis provides the foundation for hydrothermal-vent food chains—an exciting prospect because no other communities on Earth are independent of photosynthesis.

There are, however, certain difficulties with this interpretation. For example, some of the large sedentary organisms associated with vents are also found at ordinary deep-sea temperatures many meters from the nearest hydrothermal sources. This suggests that bacterial chemosynthesis is not a sufficient source of nutrition for these creatures. Another difficulty is that similarly dense populations of large deep-sea animals have been found in the proximity of "smokers"—vents where water emerges at temperatures up to 350° C. No bacteria can survive such heat, and no bacteria were found there. Unless smokers are consistently located near more hospitable warm-water vents, chemosynthesis can account for only a fraction of the vent faunas. It is conceivable, however, that these large, sedentary organisms do in fact feed on bacteria that grow in warm-water vents, rise in the vent water, and then rain in peripheral areas to nourish animals living some distance from the warm-water vents.

Nonetheless, advection is a more likely alternative food source. Research has demonstrated that advective flow, which originates near the surface of the ocean where suspended particulate matter accumulates, transports some of that matter and water to the vents. Estimates suggest that for every cubic meter of vent discharge, 350 milligrams of particulate organic material would be advected into the vent area. Thus, for an average-sized vent, advection could provide more than 30 kilograms of potential food per day. In addition, it is likely that small live animals in the advected water might be killed or stunned by thermal and/or chemical shock thereby contributing to the food supply of vents.

文章核心解读（构建 MOC）

1. 核心现象（第一段）

普通深海：动物群稀疏，以小型蠕虫、甲壳类为主，大型动物极少；

热液喷口附近：水温较高，存在高密度大型动物群（巨型蛤蜊、盲蟹、鱼类），与普通深海形成强烈反差。

2. 核心矛盾与假设（第二段）

矛盾：普通深海动物依赖表层沉降的光合作用颗粒物质为食，但喷口区域大型动物群需要数倍于普通沉降物的食物，仅靠表层沉降物无法满足；

两大食物来源假设：

（1）细菌化学合成：细菌利用化学能制造食物（早期证据：喷口水中有硫化氢、喷口细菌能进行化学合成、细菌浓度极高）；

（2）平流作用：食物从周边区域漂流或表层颗粒物质随水流输送至喷口。

3. 对主流假设的质疑（第三段）

质疑 1：部分喷口大型生物在非喷口的普通深海区域也存在，说明化学合成并非其充足营养来源；

质疑 2：“黑烟囱”（水温 350℃，无细菌存活）附近有高密度大型动物群，化学合成无法解释其食物来源（除非靠近温水喷口）。

4. 更合理结论（第四段）

平流作用是更可能的食物来源：表层悬浮颗粒物质随水流输送至喷口，中等规模喷口每天可通过平流获得超 30 千克食物；平流水中的小型动物可能因热 / 化学冲击死亡，成为额外食物。

题目

Question 1

The information in the passage suggests that the majority of deep-sea faunas that live in nonvent habitats have which of the following characteristics?

(A) They do not normally feed on particles of food in the water.

(B) They are smaller than many vent faunas.

(C) They are predators.

(D) They derive nutrition from a chemosynthetic food source.

(E) They congregate around a single main food source.

定位 MOC：第一段对比普通深海（nonvent habitats）与喷口区域的动物规模 —— 普通深海以 “tiny worms and crustaceans” 为主，喷口区域有 “huge clams, blind crabs, and fish” 等大型动物。

(A) 错误。原文明确 “大多数深海动物依赖表层沉降的颗粒物质为食”，非喷口区域动物属于深海动物，与原文矛盾；

(B) 正确。普通深海动物以小型为主，喷口区域多大型动物，可直接推断非喷口区域的大多数动物比许多喷口动物更小（符合 “纯粹推断题” 逻辑，无需额外假设）；

(C) 错误。全文未提及 “predators（捕食者）”，无中生有；

(D) 错误。化学合成是喷口动物的潜在食物来源，原文未提及非喷口动物依赖该方式；

(E) 错误。原文未说明非喷口动物是否 “聚集在单一食物来源周围”，属于主观猜测。

答案：(B)

Question 2

Which of the following does the author cite as a weakness in the argument that bacterial chemosynthesis provides the foundation for the food chains at deep-sea vents?

(A) Vents are colonized by some of the same animals found in other areas of the ocean floor.

(B) Vent water does not contain sufficient quantities of hydrogen sulfide.

(C) Bacteria cannot produce large quantities of food quickly enough.

(D) Large concentrations of minerals are found in vent water.

(E) Some bacteria found in the vents are incapable of chemosynthesis.

定位 MOC：第三段专门阐述对 “化学合成是喷口食物链基础” 的质疑（功能作用题，需识别 “质疑” 逻辑）。

(A) 正确。原文提到 “部分与喷口相关的大型固着生物也存在于海底其他区域”，说明这些生物的营养来源并非仅依赖喷口的化学合成，直接削弱题干论点；

(B) 错误。原文明确 “喷口水中发现了硫化氢”，未提及 “含量不足”，与原文矛盾；

(C) 错误。原文仅质疑化学合成 “不足以支撑所有动物”，未涉及 “产生速度”，无中生有；

(D) 错误。全文未提及 “minerals（矿物质）”，无中生有；

(E) 错误。原文提到 “许多喷口细菌具有化学合成能力”，未说 “部分细菌不具备”，偏离原文。

答案：(A)

Question 3

Which of the following is information supplied in the passage that would support the statement that the food supplies necessary to sustain vent communities must be many times that of ordinary fallout?

I. Large vent faunas move from vent to vent in search of food.

II. Vent faunas are not able to consume food produced by photosynthesis.

III. Vents are more densely populated than are other deep-sea areas.

(A) I only

(B) III only

(C) I and II only

(D) II and III only

(E) I, II, and III

定位 MOC：第二段核心矛盾 “喷口动物群需要数倍于普通沉降物的食物”，支持该观点的逻辑应为 “喷口动物消耗量大”（基础推断题，需基于原文明确信息）。

I. 错误。原文未提及喷口动物 “迁移寻找食物”，仅说部分生物在周边区域存在，无中生有；

II. 错误。原文提到喷口动物的食物来源包括表层光合作用产物（只是不足够），并非 “无法食用”，与原文矛盾；

III. 正确。第一段明确喷口区域 “remarkable densities”（密度极高），普通深海 “sparse fauna”（稀疏），密度高意味着消耗的食物更多，直接支持题干观点。

答案：(B)

Question 4

The author refers to "smokers" most probably in order to

(A) show how thermal shock can provide food for some vent faunas by stunning small animals

(B) prove that the habitat of most deep-sea animals is limited to warm-water vents

(C) explain how bacteria carry out chemosynthesis

(D) demonstrate how advection compensates for the lack of food sources on the seafloor

(E) present evidence that bacterial chemosynthesis may be an inadequate source of food for some vent faunas

定位 MOC：第三段 “smokers” 用于支撑对化学合成的质疑（功能作用题，需识别 “例证” 的逻辑目的）。

(A) 错误。热冲击提供食物是第四段平流作用的内容，与 “smokers” 无关；

(B) 错误。原文明确 “smokers 附近有大型动物” 且 “部分喷口动物存在于普通深海”，因此 “栖息地仅限于温水喷口” 错误；

(C) 错误。“smokers” 水温极高无细菌，无法解释化学合成，与原文矛盾；

(D) 错误。作者提及 “smokers” 是为了质疑化学合成，而非支持平流作用，逻辑目的偏离；

(E) 正确。“smokers” 无细菌（无法化学合成）但有高密度动物群，直接证明化学合成无法为部分喷口动物提供充足食物，符合 “质疑” 的逻辑目的。

答案：(E)

Question 5

Which of the following can be inferred from the passage about the particulate matter that is carried down from the surface of the ocean?

(A) It is the basis of bacterial chemosynthesis in the vents.

(B) It may provide an important source of nutrition for vent faunas.

(C) It may cause the internal temperature of the vents to change significantly.

(D) It is transported as large aggregates of particles.

(E) It contains hydrogen sulfide.

定位 MOC：第二段 “普通深海动物依赖表层沉降颗粒物质为食”，第四段 “平流作用输送表层颗粒物质至喷口”（纯粹推断题，需逻辑延伸）。

(A) 错误。化学合成的基础是细菌的化学能，而非表层颗粒物质，与原文矛盾；

(B) 正确。原文提到喷口动物需要数倍于普通沉降物的食物（说明普通沉降物仍是食物来源之一），且平流作用会将表层颗粒物质输送至喷口，可推断其是喷口动物的重要营养来源；

(C) 错误。原文未提及颗粒物质会 “改变喷口温度”，无中生有；

(D) 错误。原文未说明颗粒物质的输送形式（“大型聚合体”），无中生有；

(E) 错误。硫化氢是在 “喷口水中” 发现的，而非表层沉降的颗粒物质，与原文矛盾。

答案：(B)