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

a.
Pollution from the air contaminated the water supply which is what killed people.
b.
Millions of coal fires and stagnant air caused toxic fumes to build up in the air.
c.
Poor city design led to faulty ventilation in houses.
d.
Soot from forest and wildfires in the surrounding areas blew over the city.