Correct option is B
The efficiency of a lamp (also known as luminous efficacy) is defined as the amount of light output (lumens) per unit of power consumed (watts). The unit of lamp efficiency is Lumen per watt (lm/W).
The efficiency of a lamp (also known as luminous efficacy) is defined as the amount of light output (lumens) per unit of power consumed (watts). The unit of lamp efficiency is Lumen per watt (lm/W).