The study of cells has been greatly advanced by the use of an electron microscope. This is primarily because:

• A
  The resolving power of an electron microscope is $200-300 \ nm$,compared to $0.1-0.2 \ nm$ for a light microscope.
• B
  Light microscopes require thin sections,whereas electron beams can pass through thick specimens.
• C
  Electron beams have a longer wavelength than photons,making electron microscopes more powerful than light microscopes.
• D
  The electron microscope has a much higher resolving power than a light microscope.