The External Gills of an Adult Axolotl Are Not as Efficient

The external gills of an adult axolotl are not as efficient as fish gills because________.

A) water flows over the axolotl gills at many different angles
B) blood flows though the axolotl gills more slowly than through fish gills
C) axolotl gills are not highly branched
D) axolotl gills are covered by thick layers of cells
E) axolotls are slow swimmers and all fish swim fast to ventilate their gills