What was the primary cause of the London Fog of 1952

What was the primary cause of the London Fog of 1952? B. Cold air led to heavy use of coal, and the smoke from the coal fires was trapped close to the ground by a temperature inversion. ... A floating pile of oil-soaked logs in the Cuyahoga River caught fire, and the resulting media attention led to the first Earth Day.

Explanation:

it sounds like either a or c