You are presented with the question "Viruses are so small that they can be seen by what?" and the following answer choices: 
- focusing a lens
 - A computer
 - looking close
 - rays or beams
 - sunlight
 - bending light rays
 - seeing smaller
 - tuning eyes

Now knowing that viruses are so small that they can be seen only with an electron microscope and once the camera is tuned with the microscope, the focusing depends on the microscope lens, choose the best answer.


 

 focusing a lens        