Spirometry is used

Correct Answer: B

Rationale: The correct answer is B: To detect the air flow through the respiratory system. Spirometry measures lung function by assessing the volume of air inhaled and exhaled. It helps in diagnosing respiratory conditions like asthma or COPD. Choice A is incorrect because spirometry does not measure hemoglobin levels. Choice C is incorrect as spirometry does not determine the respiratory quotient, which relates to metabolic processes. Choice D is incorrect as spirometry is used for assessing respiratory function.

Correct Answer: A

Rationale: Natural killer (NK) cells are involved in innate immunity as they are able to directly kill virus-infected cells and tumor cells without prior sensitization. They are part of the body's first line of defense against infections. Plasma cells, CD8 T cells, and B memory cells are all part of adaptive immunity, which involves a specific response to pathogens and requires prior exposure. Therefore, they are not involved in innate immunity.

Correct Answer: C

Rationale: The correct answer is C: P outside < P inside. This is because pressure decreases as altitude increases. At label '8', the pressure outside the object (presumably at a higher altitude) is lower than the pressure inside the object. This is due to the decrease in air pressure with increasing altitude. Choice A is incorrect because at higher altitudes, the pressure outside is lower than inside. Choice B is incorrect as it suggests the opposite relationship. Choice D is incorrect as it does not accurately describe the relationship between the pressures at label '8'.

Correct Answer: C

Rationale: The correct answer is C (75 percent) because under quiet conditions, the venous blood returning to the heart still contains a significant amount of oxygen due to the efficient extraction of oxygen by tissues. This oxygen extraction process typically leaves around 25 percent of oxygen in the venous blood, which is then returned to the heart. Choices A (25 percent), B (50 percent), and D (90 percent) are incorrect because they do not accurately reflect the amount of oxygen retained in the blood under quiet conditions. Option A (25 percent) is the amount typically extracted by tissues, so it cannot be the correct answer. Option B (50 percent) is too high, as more oxygen is extracted by tissues. Option D (90 percent) is also too high, as it overestimates the amount of oxygen retained in venous blood.

Correct Answer: B

Rationale: The correct answer is B: a drop in tidal volume. Severing sensory fibers from the lungs would lead to decreased feedback to the brain, resulting in less inhibition of the inspiratory center and potentially overinflation of the lungs (choice C). The Hering-Breuer reflexes, responsible for preventing lung over-inflation, would disappear (choice D). However, tidal volume is primarily controlled by the respiratory muscles and respiratory center in the brain, not solely by sensory input from the lungs. Hence, severing sensory fibers would not directly lead to a drop in tidal volume.