The countercurrent exchange system found in fish gills maximizes gas exchange efficiency by:

The countercurrent exchange system found in fish gills maximizes gas exchange efficiency by:
  a. producing rapid water flows across the gill surface.
  b. allowing water and blood to come in direct contact to maximize oxygen exchange.
  c. having the most oxygen-depleted blood come in contact with the most oxygen-rich water.
  d. having the most oxygen-depleted blood come in contact with the most oxygen-depleted
  water.
  e. decreasing the oxygen content of the blood leaving the gill filaments

Question 2

Amphibians:a.
   may exchange gases across their body surfaces.
  b. all have fairly simple, book lungs.
  c. all have gills and swim bladders, homologous to those found in fishes.
  d. are characterized by having parabronchi across which most of the gas exchange occurs.
  e. have a large oxygen demand that is met by using a countercurrent gas exchange
  mechanism