SAT OwlQuestion bank / Central Ideas and Details
Long before the magnetic compass reached the Pacific, Polynesian navigators sailed thousands of kilometers between islands. They memorized the points on the horizon where particular stars rose and set, which told them their direction at night. By day, they read the angle and rhythm of ocean swells, which could reveal an island lying beyond sight by bending around it. They also watched for land-based birds such as terns, which fly out to sea to fish in the morning and return to land at dusk.
Which choice best states the main idea of the text?
Polynesian navigators found their way across the ocean by combining several kinds of natural signs.
Polynesian navigators relied mainly on the positions of stars to find their way.
Polynesian navigators traveled only during the day, when they could watch for birds and read the swells.
Polynesian navigators rarely sailed far from islands they could see.
Show answer and explanation
Answer: A
The text describes three kinds of signs: stars at night, ocean swells by day, and the flight paths of land-based birds. Together they let navigators cross thousands of kilometers, so choice A states the main idea.
Choice B is tempting because stars come first in the text, but they are only one of three sources of direction the text describes.
Why the other choices are wrong
- B. Stars are only one of the three kinds of signs in the text. Swells and birds mattered too, so "mainly" overstates the role of stars.
- C. The text says navigators used stars "at night," so they did not travel only by day.
- D. The navigators sailed thousands of kilometers and could detect islands "beyond sight," which contradicts this.
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