Correct Answer: virus

Solution : The correct option is -

Rabies is caused by a group of viruses known as the rabies virus (Rabies lyssavirus). This virus primarily infects mammals, including humans.  The virus is typically transmitted through the saliva of an infected animal, often through a bite or scratch. Once the rabies virus enters the body, it travels along nerves to the central nervous system (the brain and spinal cord), leading to the characteristic symptoms of the disease, which include neurological and behavioral changes. If left untreated, rabies can be fatal.