Which one of the following light bulb produces lowest lumens per watt?
a) incandescent
b) fluorescent
c) compact fluorescent light
d) low pressure sodium

Option A

Incandescent

Explanation:

While low pressure sodium light bulb produces the highest lumens per watt, it's incandescent light bulb that produces the lowest lumens per watt. It's important to note that incandescent lights operate at the same wattage as fluorescent lights to give out same amount of light but they produce the lowest lumens per watt compared to fluorescent lights.