Respuesta :
The answer is a)phytoplankton because the krill needs to eat the phytoplankton and the seal needs to eat the krill and so on
The answer is A phytoplankton because if there is no phytoplankton then the krill will have nothing to eat, and if the krill die out the the seals will have nothing to eat and they will also die out and so on to the sharks.