Increase in minute ventilation during exercise

Steps:

• Recall resting minute ventilation: tidal volume of 500 cm³ at 12 breaths/min equals 6000 cm³/min.
• Note exercise boosts ventilation: tidal volume rises to ~1500 cm³ and rate to ~60 breaths/min, yielding 90,000 cm³/min total.
• For moderate exercise, typical total is ~24,000 cm³/min.
• Calculate increase: 24,000 cm³/min minus 6,000 cm³/min equals 18,000 cm³/min.

Why C is correct:

• 18,000 cm³ matches the standard physiological increase in minute ventilation for moderate exercise, based on respiratory adaptations to higher oxygen demand.

Why the others are wrong:

• A: 1000 cm³ is negligible, far below exercise demands.
• B: 6000 cm³ equals resting volume, not an increase.
• D: 4000 cm³ is too low for typical exercise elevation.

Final answer: C