Which element present as an impurity in fossil fuels causes acid rain?

There are at least two elements which when burnt contribute to acid rain.

Sulfur which when burnt and mixed with rain water forms sulphuric acid H2SO4

and

Carbon which when burnt and mixed with water forms carbonic acid H2CO3

Both of these acids can be formed by burning Fossil fuels and also form naturally in the gases discharged by volcanoes.