Some words in the basic word stock are said to be stable because they_____.

A．The virus is infected into their bodies.
B．The bite of the infected animals passes the virus presenting the saliva to others.
C．The virus has established in their central nervous systems for several years.
D．The virus infect them by some infectious diseases.

A．a disease which is infectious, caused by virus of dogs and wild flesh-eating animals
B．a disease caused by evil spirits
C．a disease spread by man and all warm-blooded animals
D．a disease causes animals to be vicious and violent