TOEFL Reading Practice: A Full Sample Passage With Answer Explanations

Reading about TOEFL Reading question types only gets you so far — at some point you need to sit with an actual passage and see how the questions are built around it. Below is a short original academic-style passage followed by five questions covering the most common types, each with the reasoning behind the correct answer, not just the answer itself.

Sample Passage: Coral Bleaching

Coral reefs owe their vivid color to microscopic algae called zooxanthellae, which live within the tissue of coral polyps in a mutually beneficial relationship. The algae perform photosynthesis and share the resulting nutrients with their coral host, while the coral provides the algae with a protected environment and compounds they need for photosynthesis. This partnership is so central to reef ecosystems that most corals cannot survive without it.

When water temperatures rise even slightly above a coral's normal tolerance range, the relationship breaks down. The algae begin producing compounds that become toxic to the coral under heat stress, and the coral responds by expelling its algae. Because the algae are the source of the coral's color, this expulsion leaves the coral's white calcium carbonate skeleton visible through its now-transparent tissue — a phenomenon known as coral bleaching. A bleached coral is not dead, but it has lost its primary food source and is significantly weakened. If normal temperatures return quickly, corals can reabsorb algae and recover; if the stress continues for weeks, the coral typically starves or succumbs to disease.

Large-scale bleaching events have become more frequent since the 1980s, correlating with rising ocean temperatures. However, researchers have observed that not all coral populations bleach at the same rate under identical conditions, suggesting that some coral-algae pairings are more heat-tolerant than others. This has led to interest in whether reefs could be seeded with naturally heat-resistant algae strains to improve resilience — an approach still under active study, with early trials showing mixed results.

Question 1 — Vocabulary

The word "mutually" in the passage is closest in meaning to:

• ·(A) rarely
• ·(B) reciprocally
• ·(C) accidentally
• ·(D) permanently

Question 2 — Factual Information

According to paragraph 2, what causes a coral to expel its algae?

• ·(A) The algae stop performing photosynthesis
• ·(B) The coral's skeleton becomes visible
• ·(C) The algae produce compounds that become toxic under heat stress
• ·(D) The water becomes too cold

Question 3 — Inference

It can be inferred from the passage that a coral reef experiencing a brief spike in water temperature followed by a quick return to normal would most likely:

• ·(A) die immediately
• ·(B) never bleach at all
• ·(C) have a chance to recover its color and function
• ·(D) become more colorful than before

Question 4 — Sentence Simplification

Which of the following best expresses the essential information in this sentence from the passage: "This has led to interest in whether reefs could be seeded with naturally heat-resistant algae strains to improve resilience — an approach still under active study, with early trials showing mixed results."

• ·(A) Scientists have proven that seeding reefs with heat-resistant algae works.
• ·(B) Researchers are studying whether introducing heat-tolerant algae could help reefs, but results so far are inconclusive.
• ·(C) Reefs no longer need natural algae because of new resistant strains.
• ·(D) Early trials failed completely, so the approach has been abandoned.

Question 5 — Prose Summary

An introductory sentence for a brief summary is provided: "Coral bleaching results from a breakdown in the coral-algae relationship under heat stress." Select the THREE answer choices that express the most important ideas in the passage.

• ·(A) Zooxanthellae give coral both its color and a key source of nutrients through photosynthesis.
• ·(B) Heat stress causes algae to produce toxins, prompting coral to expel them and lose color.
• ·(C) Coral reefs are found in every ocean on Earth.
• ·(D) Some coral-algae pairings appear more heat-tolerant than others, prompting research into resilience.
• ·(E) Bleached coral always dies within a few days.
• ·(F) Zooxanthellae are visible to the naked eye.

What This Example Shows

Notice that four of the five wrong-answer patterns above are the same trap in different clothing: restating a true detail from the passage but changing its role (cause vs. effect, stated fact vs. inference, main idea vs. supporting detail), or inventing a plausible-sounding claim the passage never actually makes. Once you can spot that pattern, TOEFL Reading gets noticeably faster — you're not re-reading the whole passage for every question, you're checking each option against the specific claim it's distorting.

For the full breakdown of every TOEFL Reading question type this example touched on — vocabulary, factual information, inference, simplification, and prose summary, plus the ones not shown here like negative factual and rhetorical purpose — see our companion guide to TOEFL Reading question types.