Key: D

Core reasoning: The passage states that polar bears are adapted to the polar region and that their food chain depends on fish “found in the Arctic seas.” This directly identifies the Arctic seas as the habitat context emphasized by the text.

A. Incorrect: tropical countries are the opposite climate from the polar region described.

B. Close but less precise: the passage mentions “around the North Pole,” yet it specifically highlights dependence on organisms “found in the Arctic seas,” making the habitat answer more exact.

C. Incorrect: the passage refers to the North Pole/Arctic, not the South Pole/Antarctic.

D. Correct: “Arctic seas” is explicitly mentioned as the location where the food chain exists.

E. Incorrect: Europe is not mentioned and does not match the polar/Arctic setting.

Key: A

Core reasoning: After introducing polar bears as an example, the passage defines ecology and explains its lessons: interdependence, natural cycles, balance, human interference, and restoring balance. The whole text is an overview of ecology using examples.

A. Correct: the passage explicitly defines ecology and develops its concepts across multiple paragraphs.

B. Too narrow: polar bears appear mainly as an opening example to introduce ecological dependence.

C. Part of the text (nitrogen/oxygen cycles), but the text also covers balance, pesticides, and restoration—broader than cycles alone.

D. Only one example of human interference; not the main focus of the entire passage.

E. Mentioned, but it is one concept within ecology, not the main topic overall.

Key: D

Core reasoning: The passage states, “particularly where man interferes … the balance is destroyed.” This directly answers when ecology in an area is in danger.

A. Not supported as a “danger” condition; eating fish is part of the normal food chain described.

B. Partly true as an example, but the more general condition the passage stresses is human interference overall, not only farmers/pesticides.

C. Hypothetical and not stated; the passage does not claim this specific event as the main danger condition.

D. Correct: it matches the explicit statement about balance being destroyed when humans interfere.

E. Incorrect: plants taking nitrogen compounds is described as a normal natural cycle, not a threat.

Key: E

Core reasoning: Paragraph 3 states the “first lesson of ecology” that life in an environment depends on other forms of life, then gives the chain: polar bears → seals → fish in the Arctic seas. This is interdependence within a particular environment.

A. True detail, but it is only one link in the chain; the paragraph’s point is broader than polar bears alone.

B. Not the focus of paragraph 3; “treatment” and restoration appear later.

C. Generally true and close, but paragraph 3 emphasizes dependence among living things in one environment using a food chain example, not specifically plants-and-animals cycles (those appear in paragraph 4).

D. This belongs to paragraph 4 (oxygen cycle), not paragraph 3.

E. Correct: it captures the paragraph’s main lesson—interdependence of life in a specific area.

Key: C

Core reasoning: “Devastation” means severe damage or ruin. The closest synonym among the options is “destruction.”

A. Opposite direction: rehabilitation is recovery, not ruin.

B. Not a synonym: extinction means dying out completely (often of species), not general widespread damage.

C. Correct: destruction matches severe damage/ruin.

D. Opposite direction: preservation means protecting, not damaging.

E. Different meaning: starvation is suffering from lack of food.