Cephalochordata is the subphylum that retains all chordate characteristics, even in the adult forms.
Answer: Where it gets food.
Explanation: There is multiple tropic levels btw
The answer for this one would be A because
It helps sustain tbe population because of the food chain. everything needs to eat, so the more diverse a population is, the more options things have to eat. The population is sustained because everything is able to eat to survive