The primary causes of acid deposition are tropospheric ozone sulfur and nitrogen oxides soil dust and sand radon gas and fuel wood smoke carbon monoxide and formaldehyde

I think the correct answer would be the second option. The primary causes of acid deposition are sulfur and nitrogen oxides. Acid deposition is a term used to describe precipitation that contains acidic substances.  Sulfur oxides and nitrogen oxides present in the atmosphere would interact with water vapor and would form acids namely sulfuric acid and nitric acid. These acids are soluble in water so that when precipitation happens, these acid would be dissolved into water falling into the ground. This would cause acid rain which is very detrimental to aquatic systems like streams, lakes and wetlands. Also, it would affect the pH balance of the groundwater.