Incandescent light bulbs are notorious for being relatively inefficient in producing visible light. The tungsten wire inside such a bulb is at a temperature of approximately 3000 K and the emission spectrum is very similar to that of a blackbody. The efficiency is so low because
a) Most of the electrons are absorbed in the tungsten wire.
b) Most of the power is lost due to the resistance of the bulb.
c) The electric power actually is efficiently transformed into radiation but at 3000 K, most of it is infrared.
d) A blackbody absorbs more light than it emits, hence it appears black.