Question

why does the heart automatically adjust the flow of blood to match activity levels?
a. extreme activity damages blood cells and the body needs replacements.
b. the heart requires more oxygen when exercising.
c. it reduces the level of oxygen in the blood.
d. organs and muscles require more blood under stress.

please select the best answer from the choices provided.

○ a
○ b
○ c
○ d

Explanation:

• Option A: Extreme activity doesn't primarily damage blood cells to need replacements for blood flow adjustment.
• Option B: While the heart does need oxygen, the main reason for blood flow adjustment is to supply organs and muscles, not just the heart's own oxygen need.
• Option C: Adjusting blood flow increases oxygen delivery, not reduce it.
• Option D: During activity (stress on body), organs and muscles need more oxygen and nutrients carried by blood, so the heart adjusts flow to meet this demand.

Answer:

D. Organs and muscles require more blood under stress.