"Pure" rainfall (rainfall undisturbed by human influences) has a pH of approximately 5.6. The pH of rain in some areas has been measured at 2.6. The acidity of this rain is 1000 times that of normal rain. 10 times that of normal rain. 100 times that of normal rain. 0.5 times that of normal rain.

Ibelieve it's temperature! i'm not 100% sure.

According to arrhenius theory of acid and bases, an acid is a proton donor, while base donates hydroxyl ions. further, acid and base reacts to form salt and water.consider following example.hcl    +      h2o          →      cl-          +      h3o+here, hcl has donated a proton, hence it is an acid.now consider following reactionhcl      +      naoh            ↔      nacl      +        h2oin this reaction, hcl donates proton, hence it is acid. on other hand, naoh donates hydroxyl ion (i.e. hence it is a base.