What two acids are mainly responsible for acid rain?

Acid rain .....

The acids most responsible for acid rain are "carbonic acid" (dissolved CO2), sulfuric acid and nitric acid ... there are three.

Rain has always been acidic, long before the advent of extra gases from human activity. CO2 dissolving in water accounts for most of the acidity before the industrial revolution.

CO2(g) + H2O(l) <==> H+(aq) + HCO3^-(aq)

(Be careful with the formula "H2CO3" since there are no molecules in aqueous solution.)

In addition, some NOx produced by lightning ended up as nitric acid in ancient rain.

As man contributed to the acidity of rain, it is SO2 and NOx which end up as sulfuric acid (H2SO4) and nitric acid (HNO3) which are the major contributors to acidic rain, today. (NOx refers to various combinations of nitrogen and oxygen, like NO, NO2 and N2O4.)

H2SO3 and HNO2........

Acid rain is any form of precipitation with high levels of Nitric and Sulfuric acids.