Viruses are so small that they can be seen only with an electron microscope.
Viruses viruses are very small, a few nanometers in size.
Objects that are only a few nanometers in size can be seen only with an electron microscope.
Objects that are a few nanometers in size can be seen only with:
Options:
1. an electron microscope
2. refraction of light
3. matter vibrating
4. ultrasound
5. The bending of a ray of light
6. slight magnification
7. flashlights
8. lens