Final answer:
The plasma membrane is the structure responsible for regulating the passage of materials such as organic molecules, ions, water, oxygen, and wastes into and out of a bacterial cell. It functions by being selectively permeable, which maintains cell homeostasis through various transport mechanisms. Therefore, the correct option is C.
Step-by-step explanation:
The structure that regulates the passage of material into and out of a bacterial cell is the plasma membrane. The plasma membrane is composed of a phospholipid bilayer with embedded proteins, which separates the internal contents of the cell from its surrounding environment. This membrane is selectively permeable, allowing only certain molecules to pass through, while preventing the movement of others. Key functions of the plasma membrane include the control of the passage of organic molecules, ions, water, oxygen, and wastes. It ensures that essential substances like nutrients enter the cell while waste products are removed, maintaining cellular homeostasis. Molecules can move across this membrane via passive diffusion, facilitated transport, or active transport.