Excretion is carried out through the structure labelled

Explanation

Euglena uses a contractile vacuole to remove excess water and excrete waste. This organelle removes excess water from the cell through a process called osmoregulation. The vacuole is surrounded by smaller vacuoles that drain into it. The vacuole then empties into a reservoir, where the fluid escapes through the gullet.

From the diagram provided in the question, the contractile vacuole is labelled IV - Option C