London’s “killer fog” was ultimately the result of
a. forest fires
b. automobiles
c. dirty coal
d. heating oil

C, dirty coal.

Explanation:

London's 'killer fog', also known as the Great Smog of London of 1952, was a severe pollution in the air that occurred due to the widespread use of heating coal. The smog appeared because of the combined effects of a  period of very cold, windless weather and the usage of low-grade, dirty coal.

During the cold snap, Londoners burnt more coal than usual, using the post-war cheap version of coal. The air filled itself with a tremendous amount of sulfur dioxin which created the thick smog.

The smog caused major distraction: it reduced visibility to nearly zero, all traffic had to stop and 4000 people died by the smog's effect on the respiratory tracks.

The 'killer smog' lasted for 5 days and disappeared quickly when the weather changed.

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