Question

Predators rarely kill and eat all available prey because:

predator and prey species often occupy the same trophic level in an ecosystem
prey species often lack protective mechanisms to deter being eaten
many predator and prey species have a commensalistic relationship
predator species often will switch its prey as one prey species becomes less abundant

Answer 1

If the primary predator of a prey species is eliminated, the prey species’ population will increase to the point of overpopulating the ecosystem. This overpopulation will result in depletion of the prey species’ food supplies as more individuals compete for the same resources and can ultimately lead to the prey species starving.

Explanation: hope it helps ^w^

Answer 2

Because predator species often will switch its prey as one prey species becomes less abundant.

Why this is so should be obvious - because it's not in the interest of predators for the prey species to completely die out as it would effectively also mean that they would die out due to not having enough food to eat.