Although Several Different Drugs Are Available to Treat Malaria,many of These

Although several different drugs are available to treat malaria,many of these drugs are ineffective in certain parts of the world because:

A) malaria is difficult to diagnose accurately.
B) the organism that causes malaria has become resistant to these drugs.
C) antimalarial drugs must all be given by continuous intravenous infusion.
D) all of the above
E) none of the above