Why Don't Sulfa Drugs Target Mammalian Cells

Why don't sulfa drugs target mammalian cells?

A) Mammalian cells do not use folic acid and therefore do not have the enzyme that these drugs target.
B) Mammals make their own folic acid but use a completely different substrate to start the process and therefore sulfa drugs are unable to disrupt the process.
C) Mammals do not make their own folic acid and therefore do not have the enzyme that these drugs target.
D) Sulfa drugs do target mammalian cells but the bacteria die so quickly that the patient experiences mild symptoms but can then stop taking the medication before experiencing any serious symptoms.
E) Mammalian cells produce inhibitors to the sulfa drugs.