Answer:b. They eat other organisms to gain energy
Explanation: nutrition is one of the main characteristics of living organisms.animals need the energy from food as fuel to carry out their daily metabolic activities .
Animals depend on already made food as they cannot manufacture their own food.
Most animals feed on plants, they are called herbivores.most animals feed on other animals,they are called carnivores.most animals feed on both plant and animals,they are called omnivores.
Most animals feed on plankton on water,they are called filter feeders.most animals feed on liquid,they are called fluid feeders.
Animals mostly take solid food into their system ,they digest the food,absorb it and egest the waste.