Final answer:
Chemoautotrophs are indeed the primary producers in environments like deep sea hydrothermal vents where sunlight is not available, utilizing chemical energy from inorganic compounds for chemosynthesis.
Step-by-step explanation:
The statement that chemoautotrophs are the dominant primary producers in oxygen-deficient environments, such as the hydrothermal vents of the deep ocean floor, is TRUE. Chemoautotrophs, including certain bacteria and archaeans, thrive in extreme environments where sunlight is not available, like the dark areas of caves or the deep sea hydrothermal vents. They harness energy from inorganic compounds, particularly hydrogen sulfide (H₂S), through a process known as chemosynthesis, to create organic molecules such as glucose. This not only sustains the chemoautotrophs but also serves as a basis for the entire ecosystem's food web.