Which of the Following Statements Comparing Respiration in Fish and in Mammals

Multiple Choice

Which of the following statements comparing respiration in fish and in mammals is correct?

A) The respiratory medium for fish carries more oxygen than the respiratory medium of mammals.
B) A countercurrent exchange mechanism between the respiratory medium and blood flow is seen in mammals but not in fish.
C) The movement of the respiratory medium in mammals is bidirectional, but in fish it is unidirectional.
D) In blood, oxygen is primarily transported by plasma in fish, but by red blood cells in mammals.