Which of the following present challenges that make gas exchange more difficult for fish than for terrestrial animals? Select all that apply.
A. Water is denser and more viscous than air.
B. Water contains much less O2 than air per unit volume.
C. Gills have less surface area than lungs.
D. Unidirectional flow of water is less efficient than tidal ventilation.
E. Diffusion occurs more slowly in water than in air.

A. Water is denser and more viscous than air.

B. Water contains much less O2 than air per unit volume.

E. Diffusion occurs more slowly in water than in air.

Explanation:

The gas exchange for aquatic animals is more difficult than for terrestrial animal because of several reasons like water is denser and vicious than air so the diffusion of oxygen in air is much faster than the diffusion of oxygen in the water.  

The concentration of oxygen in the air is much higher than the concentration in the water. In air the concentration of oxygen in 21% but in water, it is a tiny fraction of 1 percent oxygen. The oxygen holding capacity of warm water becomes less in cold water. So the right answer is A, B, and E.

are there any answer choices

from the original order (top to bottom) the new order will go

1 (founder)

4 (hawk)

2 (mutate)

3 (next generation)