Which of the following is a natural cause of acid rain? a. volcano emissions, lighting, and microbial process. b. industrial emission and other man-made polluters. c. smokestacks and volcano emissions d. microbial processes and fuel combustion

A). Volcano emissions, lighting, and microbial process.

Explanation:

Acid rain is described as the rain(detrimental for environment) which is atypically acidic due to containing inflated levels of ions of hydrogen caused by the atmospheric pollution that arises due to emissions of compounds of nitrogen and sulfur-dioxide. Such rain is caused by a plenty of natural and human-made causes that lead to it.

As per the question, option A displays the natural cause of acid rain as 'volcanic emissions, lightning, and microbial process', they all emit gases naturally(nitrogen and sulfur-dioxide) that eventually precipitates into the acid rain. Thus, option A is the correct answer as the other demonstrate human-made causes.