How do the acids in rain affect tufa towers

Acid rain is slowly destroying once-resistant granite. Acid rain is created by air pollutants. ... The chemicals fall to earth as acid rain. Of all the building stones, granite is the least susceptible to acid rain because its composition is of feldspar and quartz, both of which resist attacks of acid.

answer; i believe that the correct answer is (the explosion of a nearby star(supernova);