Synthesize the information on sphingomyelin's structure to explain its role in nerve cell membranes.

• A. Sphingomyelin's structure makes it a poor insulator, hindering signal transmission.
• B. Sphingomyelin's structure makes it a poor conductor, hindering signal transmission.
• C. Sphingomyelin's structure allows it to form a protective sheath around nerve cells, aiding in signal transmission.
• D. Sphingomyelin's structure allows it to increase membrane fluidity, aiding in signal transmission.

Answer: (C)