What is the "raisin cake model" intended to explain?

As the raisin bread expands the raisins that are furthest from the local raisin became farther from the local raisin at a faster velocity than the raisins closer to the local raisin. This relates to how the universe is expanding and connects to Hubble's theory because Hubble discovered that galaxies are moving away from ours at a speed that is proportional to their distance from us. Basically the farther a galaxy is away the faster it moves away from our galaxies just like the raisins in the animation.  

The farthest raisin started off at 3cm away and after an hour was 9cm away. We can relate this to galaxies that are very distant to us for they are moving at a very fast velocity away from our galaxy.

answer; i believe its (d) intrinsic;

answersecondary succession;