Why Would It Be More Difficult to Treat Diseases in Humans

Why would it be more difficult to treat diseases in humans caused by members of the Eucarya than diseases caused by the Bacteria?

A) Multicellular organisms always have their own immune systems to contend with-so any treatment we develop needs to overcome this built-in protection mechanism in such organisms.
B) Since bacteria are so much simpler (being single-celled) , they are inherently easier to kill off than multi-cellular eukaryotic microbes.
C) Eukaryotic microbes use many of the same enzymes and systems as humans-so we lose the ability to target certain molecules that might be present ONLY in the cell type we want to eliminate. There's too much overlap when both organisms are eukaryotic.
D) Eukaryotic microbes (unlike prokaryotes) often secrete compounds that breakdown and eliminate drugs used against them. This makes them much harder to effectively eliminate than bacteria.