Viruses are so small that they can be seen only with an electron microscope.
Viruses are studied by radiography and use of the electron microscope.
Radiography is used to study viruses.
What is used to study viruses?

(a) rays or beams
(b) Cooking
(c) aqueous solution
(d) energy
(e) an image
(f) radiation
(g) radiography
(h) Dilution