Answer: Based on the description you provided, the small moving green discs that the student observed in the Elodea plant cell are most likely chloroplasts.
Chloroplasts are organelles found in the cells of plants and other photosynthesizing organisms. They are responsible for photosynthesis, the process by which plants convert sunlight into chemical energy. Chloroplasts contain chlorophyll, a pigment that absorbs light energy and converts it into chemical energy. This is why chloroplasts are often described as being green in color.
Chloroplasts are typically found in the cells of plants and algae, where they are responsible for producing energy for the organism through photosynthesis. They are found in the cytoplasm of cells, and they are typically oval or disk-shaped. They are typically small in size, and they are often described as being "in motion" due to the movement of the pigments within them.
I hope this helps! Let me know if you have any other questions.