Breathing rate increases with exercise

Steps:

• Identify the x-axis as time and y-axis as breathing rate or volume.
• Locate the rest phase: steady, low rate.
• Spot the exercise phase: sudden rise in rate.
• Match to graph showing low flat line, then upward shift.

Why A is correct:

• Graph A depicts constant low breathing rate at rest, then sharp increase during exercise, aligning with physiological demand for oxygen.

Why the others are wrong:

• B shows decreasing rate, opposite of exercise response.
• C lacks a clear transition, implying no change.
• D exhibits erratic fluctuations, not typical rest-to-exercise pattern.

Final answer: A