Final answer:
Both the lipid and protein composition can vary between membranes and contribute to function.
Step-by-step explanation:
The correct statement about membrane structure is C. Both the lipid and protein composition can vary between membranes and contribute to function.
The cell membrane is composed of a lipid bilayer primarily made up of phospholipids. The lipid composition can vary between different membranes, which influences the membrane's fluidity and permeability. Proteins are also embedded within the membrane, and their composition can also vary, allowing them to perform various functions such as transport, signaling, and structural support.