She was the fairest in the land.
or
Three:
One to write the light bulb removal program,
one to write the light bulb insertion program, and
one to act as a light bulb administrator to make sure nobody else tries to change the light bulb at the same time.
or
Because they are black and white.
or
None. Agnostics question whether electricity really exists.
or
They take short cuts!
or
A mushroom!
or
The owner got tired of the (w)hole business!
or