Final answer:
The cytoplasm functions to transport materials within the cell; however, forming a barrier around the cell and controlling material movement into and out of the cell are functions of the cell membrane, while providing energy is a role of the mitochondria.
Step-by-step explanation:
Out of the options provided, the cytoplasm primarily transports materials within the cell. The cytoplasm, a jelly-like substance called cytosol that encompasses various cellular organelles, is the site of numerous biochemical reactions that are crucial to cell function. The cytoplasm is involved in the movement of molecules throughout the cell's interior, but it does not form an external barrier or directly control the entry and exit of materials, and it does not directly provide energy to the cell. The functions described in options A, C, and D are more accurately attributed to the cell membrane (plasma membrane) and other specialized structures like the mitochondria (for energy production).