They're all common in the fact that they have to eat others that have energy, because they in themselves cannot produce their own energy. All animals are multicellular.
Answer:
I am bored too....................
Living things cannot live without eachother due to the food chain, if an animal loses it's food so will his predator and so on. Soon they will end up extinct, this is why it's important to take care of animals.
D is the best answer because c and b have nothing to do with mating and being in the same family doesn't matter