Final answer:
Phytoplankton is an autotroph, which means it can produce its own food through photosynthesis.
Step-by-step explanation:
An autotroph is an organism that can produce its own food using energy from the sun or inorganic substances. Out of the given options, phytoplankton is the only autotroph. Phytoplankton are microscopic organisms that perform photosynthesis to produce their own food. They are the foundation of marine food chains and play a crucial role in the oxygen cycle on Earth.
Learn more about Autotrophs