Question

why are yawns contagious? we asked a scientist
by teresa carey

passage text (partial):
no scientific consensus on why we yawn
theory argues that when humans are tired, we stop taking deep breaths, which
a build-up of carbon dioxide in the body, said douglas parham, a speech
st at wichita state university. a yawn might be a special kind of respiration,
said. it builds up oxygen quickly, while expelling carbon dioxide, even more
deep breath.

carbon dioxide and other chemical changes, such as a drop in oxygen or
se in a compound called adenosine, could also act as \yawn gates,\ said
giordano, a neuroethicist and neuroscientist at georgetown university.
chemicals send out a signal that triggers a yawn. by yawning, we compress
muscles of the face, driving oxygen-enriched blood to the brain, giordano said

proposals state the purpose of yawning is to cool the brain, or to stretch
nal organs like tissues and lungs, helping the body to liven up

use the passage to answer the question
what is the purpose of the transitions \one theory\ and \other proposals\ in this excerpt?
(1 point)
○ to draw a contrast between two ideas
○ to show a cause-effect relationship
○ to group together explanations to the same question
○ to point out a specific example of a general phenomenon

Explanation:

The passage is about different explanations for why we yawn. "One theory" introduces one explanation, and "other proposals" introduces additional explanations to the same question (why yawns are contagious/why we yawn). Option A is incorrect as there's no contrast; option B is incorrect as it's not about cause - effect; option D is incorrect as they are not examples of a general phenomenon. So the purpose is to group together explanations to the same question.

Answer:

C. to group together explanations to the same question