The famous _____ Gold Rush began in the U. S. in the mid-nineteen century.

A．animals will be paralysed and died after being infected with rabies.
B．In 19th century, Europeans were reinfected with rabies for the uncontrolling of wild animals.
C．All dogs were killed in Europe in the early 19th century.
D．The saliva of a rabid dog is infectious.

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.