Fact 1: Viruses are so small that they can be seen only with an electron microscope.

Fact 2: Where most viruses are DNA, HIV is an RNA virus.

Given the two facts above, answer the question "what is so small it can only be seen with an electron microscope?" with the following options: 
- clouds
 - cell
 - DNA
 - ovum
 - HIV
 - magnified
 - h2o
 - RNA


 

     HIV    