Interrelatedness can be observed in the ecosystem of Yellowtone, in which species interaction is key to maintaining a balance in the ecosystem. Option B represents a correct example of interrelatedness.
Wolves prey on elk, thereby reducing the population of elk they browse on willows. The control of the population of elk would lead to the increase of willows as well as allow for their massive growth. These willows are very important to beavers. More willows would mean more beavers. Beavers gnaw on huge willows which they use in constructing dams to slow down water flow. Beavers do not really love rivers that flow fast, and so rely on willows to make dams.
The population will be less as some will die or there are chances of equal also if no one died... Most chances are of 1st one. But it also must be the same or less. Depending on if population growth means just how much it got bigger of if it can be negative (like -8% means it got smaller by 8% and being considered "growth").