I believe that the areas are tropical and polar zones.
Answer:
The correct answer is C. benefit ... harmed
Explanation:
Predation is a type of interaction between two individuals in which one individual gets harmed which is called prey and another organism who is predator gets benefitted.
In predation, the predator kills its prey and consume it to survive. For example, Lion is a predator and deer is the prey so during predation lion kills the deer and consume it so here lions get benefited by consuming deer and deer is harmed as it lost its life. So the correct answer is C. benefit ... harmed.
D. Parasitic will be you answer.
I'm pretty sure it's high density as a solid.
I'm not exactly sure what specifically you are asking for in relationship to balancing equations, but I have some examples with working out so you can examine them and try to go through the steps with them.
Hope this helps! <3