Which of the following best describes what led to London’s “killer fog” in 1952?

Millions of homes and businesses burned coal, releasing smoke and sulfur pollution into the air. Stagnant weather trapped those pollutants near the ground, where they mixed with fog and built up to dangerous levels. This matches choice B: millions of coal fires and stagnant air caused toxic fumes to build up in the air.

AI-written and checked against the verified answer.