The answer is They were the best kind of electric light.
Explanation:  Before Edison and his team inventoried the lamp, electricity was already used to produce illumination through a system known as “arc lamps” - a current flowing between two electronic pressures and producing light.
However, this system was inefficient and generated a lot of heat. So as it could not be used anywhere like houses, shops etc. they were still lit by candles or lamps.
