Diffusion Rate Is Proportional to the Square of the Distance $\mathrm { O } _ { 2 }$

Multiple Choice

Diffusion rate is proportional to the square of the distance molecules/ions travel. Which of the following would therefore be preferable for a mid-size multicellular organism?

A) direct exchange of nutrients with the surrounding medium
B) a system for bringing nutrients into contact with cells, and another system for bringing to cells $\mathrm { O } _ { 2 }$
C) a system to circulate gases, nutrients, and wastes to and from cells
D) a system for facilitated diffusion to maximize materials that could be exchanged
E) a system of individualized exchange tubules for each cell group