Why are sulfonamides selectively toxic to bacterial cells but not human cells?

• A. Sulfonamides block ATP production within human cells.
• B. Human cells lack sterol lipids which sulfonamides target.
• C. Humans acquire folic acid through diet whereas microbes synthesize it with help from PABA.
• D. Sulfonamide prevents the transcription process within pathogenic microbes.

Answer: (C)