Vaccines Are MOST Readily Made Against

Vaccines are MOST readily made against

A) bacteria, because their cell walls remain relatively unchanged from generation to generation.
B) fungi, because several species of fungi are commensals, therefore priming the immune response to readily produce antibodies to the new vaccine.
C) helminths, because they are large organisms and make for easy targets.
D) prions, because they are new microbe so there is much research effort to stop prion-related diseases.
E) viruses, particularly RNA viruses, because their cell receptors are unchanging and bind human cell receptors.