Identify a true statement about antimalarial drugs.
a. Pyrimethamine and mefloquine have been associated with Stevens-Johnson syndrome.
b. Drugs for the treatment of acute malaria exacerbations are usually administered parenterally.
c. Primaquine inhibits the conversion of the folic acid to folinic acid in the microorganisms.
d. Pyrimethamine acts directly within the microorganisms by accumulating in the parasites and binding to the critical metabolic substances.