单项选择题

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