【单选题】

Even those most______infections of all, those caused by viruses-formerly dismissed as untreatable because viruses disappeared into the inner labyrinths of the living cells, merging into the very genomes-are now becoming______to early treatments.

A、refractory… amenable
B、malignant … indifferent
C、problematic… immune
D、benign… resistant
E、mysterious … inaccessible