Which of the following is observed in a clinical trial?
o
a. an actual patient
o
b. a dangerous situation
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c. a microscopic virus
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d. a busy hospital
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I honestly don’t know but I believe it’s A

Air enters through the nose (and sometimes the mouth), moves through the nasal cavity, the  pharynx, the  larynx, enters the  trachea, moves through the  bronchi  andbronchioles  till the alveoli.