The correct answer is d) heterotrophs.
Heterotrophs are organisms that cannot produce their own food and must rely on consuming other organisms, either plants or other animals, to obtain the necessary nutrients and energy. This contrasts with autotrophs, which can generate their own food through processes like photosynthesis or chemosynthesis.
In essence, all animals, including humans, are classified as heterotrophs because they depend on other living organisms for sustenance. Without consuming food from other sources, these animals would not be able to thrive or fulfill their energy requirements.