Which would have the most significant effect in reducing florida’s air pollution?

lowering the number of power plants
allowing only one car per family
banning fireplaces and campfires
building a widespread transit system

Building a widespread transit system would improve reduce Florida's atmospheric pollution. When public transport is improved, people are more encouraged to ride them and ditch their private transports. Having an efficient transit system would mean that less cars will be on the road, more energy will be saved, and pollution will see a dramatic decrease.

It's building a widespread transit system.