$A$ major breakthrough in the studies of cells came with the development of the electron microscope. This is because

• A
  the electron microscope is more powerful than the light microscope as it uses a beam of electrons which has a wavelength much longer than that of photons
• B
  the resolving power of the electron microscope is much higher than that of the light microscope
• C
  the resolving power of the electron microscope is $200-350 \ nm$ as compared to $0.1-0.2 \ nm$ for the light microscope
• D
  the electron beam can pass through thick materials,whereas light microscopy requires thin sections