From the story yawning together 43. Which of these is the best summary of the article?
I
e following words: faze...
awning Together to an...
A. Scientists have discovered one possible reason humans yawn. Studies indicate
that we yawn to cool our brains. This cooling process is important because a cool
brain functions more efficiently. However, this explanation is too simplistic to
serve as the definitive answer.
B. Research has shown that yawning has been observed in many species of
vertebrates. What is not clear is why this is so or what purpose yawning serves.
While some researchers indicate yawning occurs to cool the brain, others dispute
this hypothesis because of differences between humans and animals.
C. Yawning is contagious. When humans, or even dogs, see someone yawn, they
often yawn, too. Studies have found, however, that when someone just pretends
to yawn-moving his or her mouth but without making any of the
gestures--people don't yawn in response. While more studies may be needed to
explain this phenomenon, yawning isn't a very big problem.
D. Many species yawn, but the purpose served by yawning is still unknown. It is
also unclear why yawning seems to be contagious. Researchers have offered
various theories, such as yawning serves the purpose of cooling the brain or body
or expressing empathy or mimicry. However, further studies are needed before
yawning can be fully understood.