Fact 1: Viruses cannot reproduce by themselves.

Fact 2: Some smallpox viruses are maintained in laboratories.

Given the two facts above, answer the question "What cannot reproduce by itself?" with the following options: 
- Acids
 - all plants
 - anemia
 - smallpox
 - cigarettes
 - all corals
 - all bacteria
 - acetic acid


 

    smallpox     