Which lighting method was predominant in the 18th century?

The predominant lighting method in the 18th century was oil lamps. During this period, oil lamps became common in both indoor and outdoor settings, providing a safer and more efficient alternative to candles. They operated by burning oil, typically derived from animals or plants, which offered a steady and controllable light source. This was particularly important in theatres, as adequate lighting was essential for performances.

Candles, while used earlier, were less efficient due to their shorter burn time and inconsistent light output. Gas lighting, which would not become widespread until the 19th century, revolutionized lighting after this period. Incandescent bulbs had not yet been invented in the 18th century, emerging later in the 19th century. Thus, oil lamps represented the most significant advancement in lighting technology of the time, making them the correct answer.