![](https://cos-cdn.shuashuati.com/pipixue-web/2020-1231-2005-12/ti_inject-812ce.png)
'Viruses waiting for a disease' refers to ______.
A.
those viruses carried in the blood of animals
B.
some viruses which are at present harmless to man
C.
the viruses that reproduce in man without making him ill
D.
the still-not-yet-discovered viruses in the jungle