Answer:
C. A plant absorbing carbon dioxide during photosynthesis
Step-by-step explanation:
Carbon assimilation occurs when inorganic carbon (carbon dioxide) is converted to organic compounds by living organisms such as plants.
Let's analyze each choice;
The respiration of a animal - Respiration
A factory burning fossil fuels- Combustion
A plant absorbing carbon dioxide during photosynthesis- assimilation or fixation
Fossil fuel deposits - from decay of dead organisms and waste products.