Final answer:
The correct answer is option A. Heterotrophy.
Step-by-step explanation:
Animals are characterized by heterotrophy, meaning they obtain energy and carbon from food by consuming other organisms. Unlike autotrophs, which can synthesize their own nutrients through processes like photosynthesis, heterotrophs rely on consuming plants, animals, or other organic matter to meet their nutritional needs. Animals can be various types of heterotrophs such as carnivores, herbivores, omnivores, or parasites. This mode of energy acquisition differentiates them from autotrophs like plants and certain bacteria.
Protists that absorb nutrients from dead organisms are called saprobes. These are a subtype of heterotrophs that make use of organic wastes or dead matter as their source of nutrients. While animals are not capable of photosynthesis, they depend on autotrophs, either directly by consuming plants or indirectly by consuming other heterotrophs. The link between autotrophs and heterotrophs illustrates the flow of energy through an ecosystem, originating from the photosynthetic process carried out by autotrophs.