Question

by Teresa CareyThere is no scientific consensus on why we yawn.One theory argues that when humans are tired, we stop taking deep breaths, which causes a build-up of carbon dioxide in the body, said Douglas Parham, a speech scientist at Wichita State University. A yawn might be a special kind of respiration, Parham said. It builds up oxygen quickly, while expelling carbon dioxide, even more than a deep breath.Excess carbon dioxide and other chemical changes, such as a drop in oxygen or increase in a compound called adenosine, could also act as “yawn gates,” said James Giordano, a neuroethicist and neuroscientist at Georgetown University. These chemicals send out a signal that triggers a yawn. By yawning, we compress the muscles of the face, driving oxygen-enriched blood to the brain, Giordano said.Other proposals state the purpose of yawning is to cool the brain, or to stretch internal organs like tissues and lungs, helping the body to liven up.© NewsHour Productions LLC. All Rights Reserved.QuestionUse the passage to answer the question.What is the purpose of the transitions “One theory” and “other proposals” in this excerpt?(1 point)Responsesto show a cause/effect relationshipto show a cause/effect relationshipto group together explanations to the same questionto group together explanations to the same questionto point out a specific example of a general phenomenonto point out a specific example of a general phenomenonto draw a contrast between two ideasto draw a contrast between two ideas

Answer 1

The purpose of the transitions “One theory” and “other proposals” in this excerpt is **to group together explanations to the same question**. These phrases introduce different theories and proposals about the reasons why we yawn, indicating that they are addressing the same topic.