Main Idea в SAT: как найти главную мысль текста и не попасть в ловушку детали

Mycologist Dr. Lena Faust studies a soil fungus that threads through the roots of shrubs scattered across arid basins, knitting separate plants into a single underground web. Tracking shrubs during a prolonged dry spell, Faust found that individuals tied into this fungal web endured the drought far better than isolated ones nearby. The reason, she argues, is redistribution: through the fungal threads, shrubs whose roots reach deep, wetter soil pass moisture along to neighbors rooted only in the parched surface layer.

Which choice best states the main idea of the text?

1. AA soil fungus threads through desert shrubs, linking many separate plants into one underground network.
2. BThe fungal network helps connected desert shrubs survive drought by sharing water among them.
3. CDesert shrubs cannot survive a drought at all unless the soil fungus connects them to others.
4. DPassing water through the fungal network harms the deeper-rooted shrubs that supply the moisture.

In the 1950s, ornithologist Hollis Warde proposed that the tiny saffron-throated warbler flew across the open Atlantic without stopping, covering more than two thousand miles in a single flight. His contemporaries rejected the idea as impossible, insisting that a bird weighing barely twelve grams could never store enough fuel for such a journey and must instead island-hop along the coast. For decades the hypothesis was treated as a curiosity. Recently, however, ornithologist Priya Anand fitted several warblers with miniature geolocators, devices light enough not to burden the birds. The recovered data showed one warbler departing the northern shore and reappearing on the far side days later, having never touched land in between. The measurements matched precisely what Warde had once described.

Which choice best states the main idea of the text?

1. ATracking data has revived Warde's once-dismissed claim that the warbler crosses the ocean nonstop.
2. BThe geolocators Anand attached to the warblers were small enough not to hinder their flight.
3. CThe saffron-throated warbler is the longest-distance migrant of any bird species yet known.
4. DAnand's study tracked the migration routes of several different songbird species at once.

When the invasive green crab spread through Blackwell Sound, biologists welcomed the arrival of the striped hakefish, a hungry predator observed tearing into adult crabs by the dozen. Managers hoped the hakefish would blunt the invasion. But a recent survey by Okafor's team complicates that hope. The hakefish, it turns out, also devours the mudsnail-eating sculpin, a small native fish whose appetite for crab larvae had quietly suppressed each new generation of crabs. By thinning the sculpin, the hakefish removes a check on the very larvae it never eats. Whether the predator ultimately slows the crab's advance, speeds it, or leaves it unchanged now depends on a tangle of interactions no one has measured.

Which choice best states the main idea of the text?

1. ABecause the sculpin and the hakefish compete for the same crab larvae, it remains unclear whether removing either predator would ultimately help or harm the native population.
2. BAlthough the hakefish devours many adult crabs, it likely speeds the invasion, since thinning the sculpin frees more larvae than the predator could ever consume.
3. CBecause the hakefish preys on a native fish that had itself held down the crab population, its overall effect on the invasion is uncertain rather than clearly beneficial.
4. DOkafor's recent survey is notable chiefly because it documented the striped hakefish tearing into adult crabs by the dozen throughout the waters of Blackwell Sound.