Digital SAT Practice Test: Text Structure & Purpose (Set 3)

This adaptive-style simulation simulates the real Digital SAT exam interface to help you master Text Structure & Purpose.

Set 3: Text Structure

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PASSAGEScience

Penguins are birds, but they cannot fly. Instead, they use their wings as flippers. This allows them to swim very fast underwater to catch fish.

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Which choice best describes the function of the underlined sentence?