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Read the following passage and then answer the multiple-choice question that follows. The question requires to make decision regarding the revision of the reading selection.
The yawn-that irritating, ungainly, impolite disruption in board meetings, classrooms, and assembly lines all over the world-is but one of the great mysteries of humankind. Despite centuries of research, not one scientist can say with certainty why, exactly, people yawn. Oh, yes, they theorize; lines of physiologists spout their suppositions: "Excessive carbon dioxide in the lungs!" “Under-stimulated brains!" “A primal response to ward off predators!" Unfortunately, while it would be fantastic if a simple yawn could frighten away a saber-toothed tiger, the real reason for yawning is anyone's guess.
People begin expressing their boredom very early in life-even before their born. The fact that fetuses yawn tells researchers that yawning is both involuntary and not due to a general lack of oxygen, since babies in utero do not breath oxygen as adults do. Now, simply determining why babies yawn has become a part of the quest to solve the riddle of yawns. One theory that currently holds water is that yawning releases a chemical called surfactant, a substance that ensures that the alveoli, or tiny air pockets in the lungs, stay open. The production of surfactant is critical to development because it ensures that the lungs of a newborn will be ready to survive outside the womb; however, as everyone knows, the yawning continues well beyond birth.
Boring classes, office meetings, lectures, seminars, and traffic jams take quite a toll on brains, and yawning does help to revive brains to better cope with the drudgery of staying awake; however, yawning often strikes at seemingly arbitrary times. Stressful situations often beget yawns, as do colds, allergies, and sinus problems; even strenuous activity can spark excessive yawning. Experts agree that the lungs stretch during yawning, and the stretching prevents the collapse of tiny airways. This might help to explain why yawning that accompanies periods of shallow breathing, such as before and after sleeping, helps more air to enter the respiratory system. More air is good.
The seemingly arbitrary nature of yawning has prompted many scientists to suggest that yawning is actually a form of involuntary communication. Both human beings are creatures of imitation and quite receptive to suggestion; fifty-five percent of all people, in fact, will yawn within five minutes after seeing someone else yawn. Reading about yawns also has this effect, as well as talking about them and even thinking about them. Yawns also can express strong antisocial messages. Yawns are widely perceived as rude gestures. They frequently imply boredom, but yawns often accompany feelings of rejection or even anger. Some medical professionals claim that yawning is stimulated by the same chemicals in the brain that effect emotions, moods, and appetites, so perhaps to ancient ancestors, yawns were involuntary, visual signals that alerted people that it was time to seek shelter for the night, which therefore synchronized sleeping patterns. Humans are, after all, social beings.
Perhaps someday scientists will find the proper combination of theories that explains yawning once and for all. There seems to be a connection between prenatal yawns producing surfactant and adult yawns filling tiny airways in the lungs, but the ease with which humans will yawn simply because they saw someone else yawn suggests that the act is purely psychosomatic. Despite the many theories and facts pertaining to its origins, the mysterious act of yawning must join the tailbone and the appendix on the list of human anatomical conundrums.
Which choice best describes an error in the first sentence of the second paragraph?
A. subject-verb agreement
B. unnecessary commas
C. misuse of ensures
D. incorrect pronoun
E. double negative