Alight bulb is used for seeing in the dark, and conventional light bulbs generate light by heating a filament. Given these facts, what is helpful for seeing in the dark among the following options:
- an electron microscope
 - an electron lens
 - microscope
 - closing the blinds
 - blackouts
 - closing your eyes
 - focusing a lens
 - heating a filament


 

        heating a filament 