Which structure in protozoa provides flexible protection and maintains cell shape?

The pellicle is a crucial structure found in various protozoa that provides flexible protection as well as helps maintain the cell's shape. This semi-rigid layer lies just beneath the cell membrane and gives structure to the organism, allowing it to withstand external pressures while still retaining some flexibility.

Additionally, the pellicle plays a significant role in the mobility of protozoa, particularly in organisms with flagella or cilia, as it allows for coordinated movement without losing shape. Unlike a rigid cell wall, the pellicle's adaptability is essential for the survival of these organisms in varied environments, making it vital for their overall functionality.

The other options presented in the question serve different purposes; for example, pseudopodia are extensions that assist in movement and feeding but do not function in structural support. Cysts are protective forms that protozoa take under harsh conditions but aren’t involved in day-to-day cell shape maintenance. Lastly, eyespots are light-sensitive structures that aid in navigation by detecting light but do not contribute to the physical integrity or protection of the cell. Each of these structures is important in its own right, but the pellicle distinctly fulfills the role of providing flexible protection and maintaining cell shape.