iBT TOEFL Topic Vocabulary Breakthrough Unit 079

iBT TOEFL Topic Vocabulary Breakthrough Unit 079
Author: Li Xiaolai

79. Instead of heavy jaws with teeth, modern birds have toothless, lightweight jaws, called beaks or bills. The eyes of birds are protected by three eyelids: an upper lid resembling that of humans, a lower lid that closes when a bird sleeps, and a third lid, called a nictitating membrane, that sweeps across the eye sideways, starting from the side near the beak. This lid is a thin, translucent fold of skin that moistens and cleans the eye and protects it from wind and bright light.

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