[单选题]
2. Which of the following f+5p4 tlpkb3tzo5 xp/l actors complicatessqy)r yy h/*vs(s z))n the treatment of human viral infects)v)/q*y)n z (y hrsysions?
A. RNA genetic material.
B. Rapid evolution by mutation
C. Slow evolution by mutation.
D. Viral infections are usually fatal.
