I think its A- independence
I'd have to say either 1 or 3. I would choose number 3.
This simple concept describes the process by which cells exchange toxic gases for life-sustaining gases. It also describes how nerve cells are able to send electrical signals to each other cells. Diffusion tells embryonic cells where to crawl and when they have arrived. Diffusion also makes it possible to reduce the loss of body heat to the surrounding environment.
