Sources of Acid Rain. Acid rain is caused by a chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. These substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain. Sulfur dioxide and nitrogen oxides dissolve very easily in water and can be carried very far by the wind. As a result, the two compounds can travel long distances where they become part of the rain, sleet, snow, and fog that we experience on certain days. Human activities are the main cause of acid rain.
iOS is Apple's proprietary mobile operating system (OS) for its handheld devices, such as the iPhone, iPad and iPod Touch. The operating system is based on the Macintosh OS X.
A mobile application software or mobile app is an application software designed to run on mobile devices such as smartphones and tablet computers.