Which of the following events could shift the demand curve for gasoline to the left? a

The correct answer is: c. Public service announcements are run on television, encouraging people to walk or ride bicycles instead of driving cars.

A shift in the demand curve happens when the quantity demanded decreases or increases at each price level. This happens when other factors influencing the demanded apart from the own-price.

If there's a public announcement on TVs that encourage people to walk or ride bicycles rather than driving cars, this means that people will use cars less often. As a result, the demand for gasoline will decrease, causing the demand curve to shift to the left.