Problem:
Question: What is a limitation of the fish circulatory system?
a. Blood is pumped to the gills with too high a blood pressure and this sometimes reverses the counter-current flow of blood and water across the gills
b. Blood that reaches the heart is O2-poor, so keeping the heart muscle itself well oxygenated can be a limitation for strenuous swimming c. Blood is pumped to the tail muscles with too low a blood pressure for extended muscular effort
d. O2-poor blood is not pumped directly from the heart to the gills
Please provide correct answer.