Flagella allow movement of cell. Some prokaryotic cells do have flagella that enable movement of cells.
For example, the flagella of choanocytes draws water in through its collar made of small hair-like projections resembling a fence. This fence traps the food particles in the water, such as protists and tiny animals.
Thus, the options (b), (c) and (d) are incorrect.
Flagella allow movement of cell. Some prokaryotic cells do have flagella that enable movement of cells.
Therefore, the correct option is – a. movement of the cell.