# GMAT 考满分题库

The trophic contamination hypothesis posits that shorebirds accumulate industrial and urban pollution at stopover sites, toxins that are subsequently released in sudden high doses as fat is burned during migratory flights, disrupting the birds ability to make migratory decisions. For example, large contaminant doses might hamper refueling by altering the satiation signal in shorebirds so that they do not accumulate sufficient fat for migration. A recent study found that, out of those shorebirds that were unable to migrate, some weighed as much as 20% less than the average migrating bird of their species. Whether such findings are a result of shorebirds suffering from trophic contamination, or whether such birds simply cut their migrations short by landing in a foreign ecosystem, is unlikely to be resolved until further studies are conducted.

One promising line of research involves organochlorines, toxins deposited on mudflats in the 1970s and 1980s, now buried by sediments but finally close enough to the surface to be of issue to foraging shorebirds. Organochlorines should be more accessible to long-billed shorebirds that probe deeply for prey than to short-billed species that forage at or near the surface. We predict that an increased number of long-billed shorebirds will either be unable to migrate or will be found along an aberrant flight path.

According to the passage, the author implies that foreign ecosystems have which potential effect on shorebirds?

• AThey can make a bird more vulnerable to predators.
• BThey can expose shorebirds to foreign toxins.
• CThey can diminish a birds ability to navigate.
• DThey can lead to a reduction in the bird`s weight.
• EThey can cause a bird to become separated from its flock.

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