Passage Reference: . Bird-watchers aren't the only ones keeping close tabs on feathered migrants this spring. Public-health officials, fearing a resurgence of the imported virus that gave both birds and people West Nile Fever last summer, are scanning the skies for signs of avian ill health. But biologists warn that sickly birds, beyond being harbingers of human disease, warrant concern in their own right. Last year's West Nile outbreak, which killed seven elderly people, also felled 5,000 to 10,000 native birds - mostly crows but 19 species in all, including robins, blue jays, herons, hawks, and kingfishers.

Tips: When a paragraph says something is important "in its own right", that often points to the main idea.

Why the other options are wrong:

• West Nile Fever: This heading focuses on one disease, but the paragraph's main idea is broader - concern about bird health overall. This is an example-as-main-idea trap.
• Extinctions due to infectious diseases: Bird deaths are mentioned, but extinction is not claimed. This is a partial truth trap.

Key Vocabulary:

• harbingers = warning signs
• felled = killed

Question Focus: Main idea - diseases are increasing because of global movement

Passage Reference: B. That's not surprising. Just as measles and smallpox carried to the New World by Spanish conquistadors took a devastating toll on Native Americans who had never been exposed to the germs, transporting domestic and wild animals from one place to another introduces native creatures to new, and often deadly, infectious diseases. As globalization shuffles more people, animals, and pathogen-contaminated products around the world, biologists say such infections are increasing. According to Peter Daszek of the University of Georgia's Institute of Ecology in Athens, 'There is probably no place on Earth that is free from pathogen pollution.' C.

Why this is correct: The paragraph clearly says that infections are increasing because globalization moves people, animals, and germs around the world. The quote about no place being free from pathogens reinforces this growing problem.

Tips: Look for clear trend words like "increasing" to match headings about change over time.

Why the other options are wrong:

• The humans' fault: Humans are involved, but the main focus is the increase of disease, not blaming humans directly. This is a context shift trap.
• The major cause of new wildlife diseases: Causes are discussed later in more detail. Here, the focus is on the trend, not the main cause. This is a wrong section trap.

Key Vocabulary:

• devastating = very damaging
• pathogen = disease-causing organism

Question Focus: Main idea - wildlife diseases threaten animals and humans

Passage Reference: C. In a report published last winter in Science, Daszek documents dozens of 'emerging' wildlife diseases - from elk stricken with bovine tuberculosis to Antarctic penguins who show signs of exposure to a chicken virus. He believes such diseases pose a significant, yet largely unrecognized, threat to global biodiversity. And the spread of some wildlife infections also endangers human health. In last week's Science, researchers warn that seals just discovered to be infected with influenza B could spawn a new flu epidemic among humans.

Why this is correct: The paragraph directly states that emerging diseases are a threat to biodiversity and endanger human health. Both parts of the heading are clearly covered.

Tips: If a paragraph links animals and humans together, look for a heading that includes both.

Why the other options are wrong:

• Extinctions due to infectious diseases: Some animals are sick, but extinction is not stated here. This is a paraphrase trap.
• Unknown causes: The causes are not the focus. The focus is on impact, not mystery. This is a context shift trap.

Key Vocabulary:

• emerging = newly appearing
• biodiversity = variety of life

Question Focus: Main idea - human actions create unnatural disease outbreaks

Passage Reference: s. D. Like predators, pathogens are natural components of ecosystems that help regulate wildlife populations. But humans cook up host-pathogen combinations that could never occur in nature. One early example was the introduction of cattle to Africa in the late 1800s, which sparked an epidemic of a virus called rinderpest among native buffalo, wildebeest, and other grazers. So many of these animals died that large swaths of natural savanna turned into scrubby forest.

Why this is correct: The paragraph contrasts natural disease with human-created combinations and gives a clear example caused by humans. The message is that people are responsible.

Tips: Pay attention to contrast words like "but" - they often signal the main idea.

Why the other options are wrong:

• Extinctions due to infectious diseases: Many animals died, but extinction is not the main point. The cause, human action, is. This is a partial truth trap.
• The major cause of new wildlife diseases: This paragraph gives one example, not the overall main cause. This is an example-as-main-idea trap.

Key Vocabulary:

• regulate = control
• sparked = caused

Question Focus: Main idea - spillover from domestic animals

Passage Reference: est. E. Indeed, spillover of pathogens from domestic livestock and pets may be the leading cause of emerging wildlife diseases, especially as humans encroach increasingly on wild-animal habitat. In the western United States, the black-footed ferret was nearly wiped out by distemper, a deadly viral disease of domestic dogs. African wild dogs in the Serengeti did die out after exposure to canine distemper. Today Africa's endangered mountain gorillas are threatened by several diseases, from measles to the common cold, that they catch directly from human tourists.

Why this is correct: The paragraph clearly says spillover may be the leading cause of new wildlife diseases and gives several strong examples.

Tips: Headings with words like "major cause" usually match paragraphs that explain reasons.

Why the other options are wrong:

• The humans' fault: Humans are involved, but the heading is too general. This paragraph focuses on one main cause. This is a context shift trap.
• Extinctions due to infectious diseases: Some species died out, but extinction is not the main theme. This is a detail trap.

Key Vocabulary:

• spillover = spread from one group to another
• encroach = move into

Question Focus: Main idea - disease spreading back to domestic animals

Passage Reference: rists. F. Sometimes, this process reverses itself in what Daszek calls 'spill back'. A disease known as brucellosis, for example, was probably introduced to North America along with cattle. But infected bison roaming Yellowstone National Park are now considered a threat to livestock, and are often shot by ranchers when they wander outside park boundaries.

Why this is correct: The paragraph explicitly says the process reverses and explains how disease spreads back from wildlife to livestock.

Tips: When the paragraph defines a special term, that term often matches the heading.

Why the other options are wrong:

• The major cause of new wildlife diseases: This is about reverse spread, not the main cause. This is a reverse meaning trap.
• The humans' fault: Humans respond by shooting animals, but the main idea is reversal, not blame. This is a context shift trap.

Key Vocabulary:

• reverses = goes the other way
• threat = danger

Question Focus: Main idea - habitat loss causes disease outbreaks

Passage Reference: ndaries. G. Destroying habitat is another way humans spawn disease outbreaks. The loss of US wetlands has crowded ducks, geese, and other waterfowl into smaller bodies of water, sparking epidemics of cholera and botulism that kill tens of thousands of birds at a time. According to Robert McLean, director of the US Geological Survey National Wildlife Health Center, 'Shrinking habitat is also deteriorating, which promotes growth of bacteria and other pathogens.' H.

Why this is correct: The paragraph explains how habitat loss crowds animals, which leads to disease outbreaks. This clearly matches reduced habitat.

Tips: If a paragraph starts by naming a cause, that cause is usually the heading.

Why the other options are wrong:

• The humans' fault: Humans are involved, but the focus is on habitat reduction, not blame. This is a context shift trap.
• Infectious diseases on the rise: Diseases are mentioned, but the cause here is habitat loss, not overall increase. This is a wrong section trap.

Key Vocabulary:

• wetlands = land with a lot of water
• deteriorating = getting worse

Question Focus: Main idea - mysterious diseases with suspected human links

Passage Reference: athogens.' H. Occasionally, the culprit behind an emerging wildlife illness is a mystery. In 1998, biologists identified a new fungal disease that was killing huge numbers of frogs in remote upland rain forests of Australia and Central America. Since then, the same fungus has been fingered in die-offs of boreal toads in the Colorado Rockies. But even in these cases, Daszek suspects people are ultimately to blame. One possibility is that global warming, which has increased the number of dry days in tropical cloud forests, concentrated water-loving frogs in too small a habitat, sparking disease outbreaks similar to those rampant

Why this is correct: The paragraph begins by saying the cause is a mystery, even though humans may still be involved indirectly.

Tips: Opening sentences often signal the main idea very clearly in Matching Headings.

Why the other options are wrong:

• Reduced habitat: Habitat is mentioned later, but the main focus is unknown cause. This is an example-as-main-idea trap.
• The humans' fault: Humans are suspected, not proven. The paragraph stresses uncertainty. This is a qualification trap.

Key Vocabulary:

• culprit = cause
• die-offs = mass deaths

General Tips:

• Read all headings first and underline key words like cause, increase, mystery, or reverse.
• Always choose the heading that matches the main idea, not one interesting detail.
• Headings follow paragraph order, so use the previous answer to guide you.
• If a heading fits only one sentence, it is probably wrong.