Final answer:
The correct answer is option b) 1879.
Step-by-step explanation:
The lightbulb became open to the public in 1879 when Thomas Edison patented the practical incandescent light bulb. Edison's invention rapidly made its way into homes and factories, revolutionizing the way people lived and worked. The establishment of the first commercial power plants in 1882, along with Nikola Tesla's development of the AC (alternating current) system, enabled electricity to reach further and cover larger urban areas.
Edison's electrical systems initially used direct current (DC), but the AC system developed by George Westinghouse eventually prevailed and became the primary method for electrical distribution by 1892.