The correct option is A Viruses
Smallpox disease is a serious, highly contagious, and often life-threatening infection marked by a rash of round pox (blisters) on the face, arms, and legs. It is caused by the Variola virus. The last case of smallpox in the United States was in 1949.
Rabies is a viral disease that causes acute inflammation of the brain in humans and other warm-blooded animals.
Therefore, the correct answer is option A.