The correct answer is: A. Autotrophs.
Autotrophs are organisms that can produce their own food using inorganic materials and energy from sunlight or other sources. They are the primary producers in an ecosystem, and they provide food for other organisms.
Hetertrophs are organisms that cannot produce their own food, and they must consume other organisms or organic matter to survive. They are the secondary, tertiary, and quaternary consumers in an ecosystem.
Auxotrophs are organisms that require a specific nutrient or nutrients that they cannot synthesize themselves. They are often used in research to study the function of genes and proteins.
Saprotrophs are organisms that decompose dead organic matter. They are important in the recycling of nutrients in an ecosystem.
Here is a table that summarizes the characteristics of each type of organism:
| Type of organism | Can produce own food? | Source of energy | Example |
| — | — | — | — |
| Autotroph | Yes | Sunlight or other inorganic sources | Plants, algae, some bacteria |
| Heterotroph | No | Other organisms or organic matter | Animals, fungi, most bacteria |
| Auxotroph | No | Specific nutrients that they cannot synthesize themselves | Many bacteria and fungi |
| Saprotroph | No | Dead organic matter | Fungi, some bacteria |