Based on the information in the passage, the best choices for causes 4 and 5 are:
B. to build up oxygen
E. to cool the brain
These options align with the theories presented in the passage regarding the functions of yawning.
There 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.
Effect: We yawn. Cause 1: to quickly expel carbon dioxide. Cause 2: to drive oxygen-enriched blood to the brain. Cause 3: to stretch internal organs. Based on the information in the passage, what are the best choices for causes 4 and 5? Select both correct answers.
A. to increase the frequency of deep breaths
B. to build up oxygen
C. to increase adenosine levels
D. to compress facial muscles
E. to cool the brain
1 answer