Question

PART 1:  The FEV1/VC ratio is clinically significant because it is an indicator of ["alveolar surface area", "airway resistance", "alveolar pressure", "respiratory rate"] . A healthy individual's FEV1/VC ratio is near ["50%", "80%", "90%", "100%"], while an individual with an obstructive lung disease will likely have a FEV1/VC ratio of less than ["50%", "80%", "90%", "100%"] because of a ["decrease in resistance", "merging", "dilation", "collapsing"] of the small airways.

PART 2: Tidal volume increased after exercise because CO2 production ["increased", "decreased"]  owing to the increased metabolic rate of exercising skeletal muscle. This change in CO2 stimulated the ["peripheral", "central"] ["baroreceptors", "photoreceptors", "osmoreceptrs", "chemoreceptors"] resulting in ["faster", "slower"] and  ["shallower", "deeper"] breathing. As a result of the tidal volume increasing, inspiratory and expiratory volumes both ["significantly increased", "significantly decreased", "did not significantly change"] while vital capacity ["significantly increased", "significantly decreased", "did not significantly change"]. Since total lung capacity is equal to the vital capacity plus residual volume (which is a constant), total lung capacity  ["significantly increased", "significantly decreased", "did not significantly change"]      .

Answer 1

Answer Part 1:

The FEV1/VC ratio is clinically significant because it is an indicator of "airway resistance". A healthy individual's FEV1/VC ratio is near "80%", while an individual with an obstructive lung disease will likely have a FEV1/VC ratio of less than "80%" because of a "collapsing" of the small airways.

Explanation: FEV1 is the amount of air which can be forced out from lungs in one second. VC is maximum amount of air one can expel out from lungs after inhalation. The ratio FEV1/VC indicates airway resistance or airflow obstructions. When the lumen of the airway becomes narrow then it offers resistance to the flow of air in the airway. If FEV1/VC is 70% to 80% then it's normal for healthy individuals but if the FEV1/VC is less than 0.7 (70%) then it indicates obstructive lung disease. When the small airway collapses the resistance to flow of air increases which happens in emphysema and COPD. In such case of COPD, FEV1and VC both reduces, hence the ratio FEV1/VC also decreases i.e it comes below 70% in mild cases and further below in moderate to severe cases. As the above values are close to 80% in the choice of answers, I have opted for 80%.